Chemical weapons experts blocked from Syrian attack site, UK says

(CNN)They've waited two days to enter the site of the latest suspected chemical attack, where dozens of Syrian civilians were killed.

But despite having UN clearance, the Organization for the Prohibition of Chemical Weapons still can't enter the city of Douma, UK officials said.

The United Kingdom said Syria and Russia have blocked OPCW investigators from entering Douma, and the United States said Russia may have tampered with evidence at the site.

A representative of Russia's military said late Monday that OPCW inspectors would be permitted to travel to Douma on Wednesday.

"Wednesday is when we expect the arrival of the OPCW experts and Russia is not preventing this in any way," Igor Kirillov told journalists at The Hague.

Russia said its security forces would assist the OPCW inspectors.

Also Monday, Russia's envoy to the OPCW, Alexander Shulgin, released a statement accusing the the Syrian Civil Defense White Helmets of using US funds to fake the suspected chemical attack.

A year after the US first attacked Syria, what's changed?

A year after the US first attacked Syria, what's changed?

The OPCW team is tasked with determining whether banned substances were used in the attack, a claim that both Syria and its most powerful ally, Russia, have vehemently denied.

The team has been in Syria since Saturday, the same day the United States, United Kingdom and France carried out airstrikes against Syrian government targets in response to the April 7 attack in Douma.

Survivors of Syria chemical attack tell their stories for the first time

Survivors of Syria chemical attack tell their stories for the first time

Western leaders have blamed the Syrian government for the Douma attack, which killed about 75 people, including children, UK officials said.

Another 500 people were treated for symptoms consistent with chemical weapons exposure, the World Health Organization reported, citing its partners on the ground.

Syria's Deputy Foreign Minister Fayssal Mikdad said Monday his country was ready to facilitate the OPCW team in any way to carry out its mission, the state-run SANA news agency reported.

But Kremlin spokesman Dmitry Peskov did not respond directly to CNN's question on whether Russia had blocked the experts. Peskov said only that Russia was against "groundless" accusations about who was responsible for the attack.

Russian Deputy Foreign Minister Sergei Ryabkov said the OPCW team's arrival was hampered by the weekend airstrikes, state media RIA Novosti reported.

An injured man is helped following an airstrike in Aleppo's Maadi neighborhood on December 17, 2013.

Photos: Syria's civil war, in pictures

An injured man is helped following an airstrike in Aleppo's Maadi neighborhood on December 17, 2013.

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A man holds a baby who was rescued from rubble after an airstrike in Aleppo on February 14, 2014.

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A man holds a baby who was rescued from rubble after an airstrike in Aleppo on February 14, 2014.

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A US ship staff member wears personal protective equipment at a naval airbase in Rota, Spain, on April 10, 2014. A former container vessel was fitted out with at least $10 million of gear to let it take on about 560 metric tons of Syria's most dangerous chemical agents and sail them out to sea, officials said.

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A US ship staff member wears personal protective equipment at a naval airbase in Rota, Spain, on April 10, 2014. A former container vessel was fitted out with at least $10 million of gear to let it take on about 560 metric tons of Syria's most dangerous chemical agents and sail them out to sea, officials said.

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A Free Syrian Army fighter fires a rocket-propelled grenade during heavy clashes in Aleppo on April 27, 2014.

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A Free Syrian Army fighter fires a rocket-propelled grenade during heavy clashes in Aleppo on April 27, 2014.

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A giant poster of al-Assad is seen in Damascus on May 31, 2014, ahead of the country's presidential elections. He received 88.7% of the vote in the country's first election after the civil war broke out.

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A giant poster of al-Assad is seen in Damascus on May 31, 2014, ahead of the country's presidential elections. He received 88.7% of the vote in the country's first election after the civil war broke out.

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Rebel fighters execute two men on July 25, 2014, in Binnish, Syria. The men were reportedly charged by an Islamic religious court with detonating several car bombs.

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Rebel fighters execute two men on July 25, 2014, in Binnish, Syria. The men were reportedly charged by an Islamic religious court with detonating several car bombs.

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Photographs of victims of the Assad regime are displayed as a Syrian army defector known as "Caesar," center, appears in disguise to speak before the House Foreign Affairs Committee in Washington. The July 31, 2014, briefing was called "Assad's Killing Machine Exposed: Implications for U.S. Policy." Caesar, apparently a witness to the regime's brutality, smuggled more than 50,000 photographs depicting the torture and execution of more than 10,000 dissidents. CNN cannot independently confirm the authenticity of the photos, documents and testimony referenced in the report.

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Photographs of victims of the Assad regime are displayed as a Syrian army defector known as "Caesar," center, appears in disguise to speak before the House Foreign Affairs Committee in Washington. The July 31, 2014, briefing was called "Assad's Killing Machine Exposed: Implications for U.S. Policy." Caesar, apparently a witness to the regime's brutality, smuggled more than 50,000 photographs depicting the torture and execution of more than 10,000 dissidents. CNN cannot independently confirm the authenticity of the photos, documents and testimony referenced in the report.

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Volunteers remove a dead body from under debris after shelling in Aleppo on August 29, 2014. According to the Syrian Civil Defense, barrel bombs are now the greatest killer of civilians in many parts of Syria. The White Helmets are a humanitarian organization that tries to save lives and offer relief.

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Volunteers remove a dead body from under debris after shelling in Aleppo on August 29, 2014. According to the Syrian Civil Defense, barrel bombs are now the greatest killer of civilians in many parts of Syria. The White Helmets are a humanitarian organization that tries to save lives and offer relief.

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Medics tend to a man's injuries at a field hospital in Douma after airstrikes on September 20, 2014.

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Medics tend to a man's injuries at a field hospital in Douma after airstrikes on September 20, 2014.

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A long-exposure photograph shows a rocket being launched in Aleppo on October 5, 2014.

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A long-exposure photograph shows a rocket being launched in Aleppo on October 5, 2014.

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Rebel fighters dig caves in the mountains for bomb shelters in the northern countryside of Hama on March 9, 2015.

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Rebel fighters dig caves in the mountains for bomb shelters in the northern countryside of Hama on March 9, 2015.

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Nusra Front fighters inspect a helicopter belonging to pro-government forces after it crashed in the rebel-held Idlib countryside on March 22, 2015.

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Nusra Front fighters inspect a helicopter belonging to pro-government forces after it crashed in the rebel-held Idlib countryside on March 22, 2015.

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A Syrian child fleeing the war gets lifted over fences to enter Turkish territory illegally near a border crossing at Akcakale, Turkey, on June 14, 2015.

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A Syrian child fleeing the war gets lifted over fences to enter Turkish territory illegally near a border crossing at Akcakale, Turkey, on June 14, 2015.

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A refugee carries mattresses as he re-enters Syria from Turkey on June 22, 2015, after Kurdish People's Protection Units regained control of the area around Tal Abyad, Syria, from ISIS.

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A refugee carries mattresses as he re-enters Syria from Turkey on June 22, 2015, after Kurdish People's Protection Units regained control of the area around Tal Abyad, Syria, from ISIS.

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A sandstorm blows over damaged buildings in the rebel-held area of Douma, east of Damascus, on September 7, 2015.

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A sandstorm blows over damaged buildings in the rebel-held area of Douma, east of Damascus, on September 7, 2015.

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Members of a Syrian opposition group attack the headquarters of al-Assad regime forces in the Aleppo villages of Nubul and al-Zahraa on February 12, 2016.

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Members of a Syrian opposition group attack the headquarters of al-Assad regime forces in the Aleppo villages of Nubul and al-Zahraa on February 12, 2016.

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This still image, taken from a video posted by the Aleppo Media Center, shows a young boy in an ambulance after an airstrike in Aleppo, Syria, on August 17, 2016. It took nearly an hour to dig the boy, identified as Omran Daqneesh, out from the rubble, an activist told CNN. The airstrike destroyed his home, where he lived with his parents and two siblings. Director of the Aleppo Media Center Yousef Saddiq said Omran's 10-year-old brother, Ali, died from his injuries.

Photos: Syria's civil war, in pictures

This still image, taken from a video posted by the Aleppo Media Center, shows a young boy in an ambulance after an airstrike in Aleppo, Syria, on August 17, 2016. It took nearly an hour to dig the boy, identified as Omran Daqneesh, out from the rubble, an activist told CNN. The airstrike destroyed his home, where he lived with his parents and two siblings. Director of the Aleppo Media Center Yousef Saddiq said Omran's 10-year-old brother, Ali, died from his injuries.

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Smoke rises after an airstrike in Aleppo on October 4, 2016.

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Smoke rises after an airstrike in Aleppo on October 4, 2016.

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Arabic writing that reads "some day we will return" is seen on a bus window as civilians evacuate Aleppo on December 15, 2016. The evacuations began under a new ceasefire between rebels and pro-government forces.

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Arabic writing that reads "some day we will return" is seen on a bus window as civilians evacuate Aleppo on December 15, 2016. The evacuations began under a new ceasefire between rebels and pro-government forces.

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This photo, provided by the activist Idlib Media Center, shows dead children after a suspected chemical attack in the rebel-held city of Khan Sheikhoun on April 4, 2017. Dozens of people were killed, according to multiple activist groups. The United States responded a few days later by launching between 50-60 Tomahawk missiles at a Syrian government airbase. US officials said the base was home to warplanes that carried out the chemical attack. Syria has repeatedly denied it had anything to do with the attack.

Photos: Syria's civil war, in pictures

This photo, provided by the activist Idlib Media Center, shows dead children after a suspected chemical attack in the rebel-held city of Khan Sheikhoun on April 4, 2017. Dozens of people were killed, according to multiple activist groups. The United States responded a few days later by launching between 50-60 Tomahawk missiles at a Syrian government airbase. US officials said the base was home to warplanes that carried out the chemical attack. Syria has repeatedly denied it had anything to do with the attack.

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Members of the UN Security Council raise their hands on April 12, 2017, as they vote in favor of a draft resolution that condemned the reported use of chemical weapons in Syria.

Photos: Syria's civil war, in pictures

Members of the UN Security Council raise their hands on April 12, 2017, as they vote in favor of a draft resolution that condemned the reported use of chemical weapons in Syria.

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Residents of the war-torn city of Douma break their Ramadan fast on June 18, 2017.

Photos: Syria's civil war, in pictures

Residents of the war-torn city of Douma break their Ramadan fast on June 18, 2017.

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A member of the Syrian pro-regime forces fires a machine gun as a comrade holds his feeding ammunition belt on November 11, 2017. It was during an advance toward rebel-held positions west of Aleppo.

Photos: Syria's civil war, in pictures

A member of the Syrian pro-regime forces fires a machine gun as a comrade holds his feeding ammunition belt on November 11, 2017. It was during an advance toward rebel-held positions west of Aleppo.

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A child receives medical treatment after a village was attacked in the rebel-held Eastern Ghouta region on February 25, 2018. Several people were treated for exposure to chlorine gas, opposition groups said, as airstrikes and artillery fire from the regime continued. CNN was unable to independently verify claims that chlorine was used as a weapon.

Photos: Syria's civil war, in pictures

A child receives medical treatment after a village was attacked in the rebel-held Eastern Ghouta region on February 25, 2018. Several people were treated for exposure to chlorine gas, opposition groups said, as airstrikes and artillery fire from the regime continued. CNN was unable to independently verify claims that chlorine was used as a weapon.

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Bodies lie on the ground in the rebel-held city of Douma, Syria, on April 8, 2018. <a href="https://www.cnn.com/2018/04/11/middleeast/syria-chemical-attack-500-affected-who-intl/index.html" target="_blank">According to activist groups,</a> helicopters dropped barrel bombs filled with toxic gas on Douma, which has been the focus of a renewed government offensive that launched in mid-February. The Syrian government and its key ally, Russia, vehemently denied involvement and accused rebel groups of fabricating the attack to hinder the army's advances and provoke international military intervention.

Photos: Syria's civil war, in pictures

Bodies lie on the ground in the rebel-held city of Douma, Syria, on April 8, 2018. According to activist groups,helicopters dropped barrel bombs filled with toxic gas on Douma, which has been the focus of a renewed government offensive that launched in mid-February. The Syrian government and its key ally, Russia, vehemently denied involvement and accused rebel groups of fabricating the attack to hinder the army's advances and provoke international military intervention.

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Damascus skies erupt with anti-aircraft fire as the US and its allies launch an attack on Syria's capital early on April 14, 2018. US President Donald Trump announced airstrikes in retaliation for Syria's alleged use of chemical weapons. Trump says the strikes are part of a sustained military response, in coordination with France and the United Kingdom.

Photos: Syria's civil war, in pictures

Damascus skies erupt with anti-aircraft fire as the US and its allies launch an attack on Syria's capital early on April 14, 2018. US President Donald Trump announced airstrikes in retaliation for Syria's alleged use of chemical weapons. Trump says the strikes are part of a sustained military response, in coordination with France and the United Kingdom.

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Displaced Syrian residents wait to receive food aid distributed by the UN Relief and Works Agency at the besieged al-Yarmouk camp, south of Damascus, Syria, on January 31, 2014. According to the UN Envoy for Syria, an estimated 400,000 Syrians have been killed since an uprising in March 2011 spiraled into civil war. See how the conflict has unfolded.

Photos: Syria's civil war, in pictures

Displaced Syrian residents wait to receive food aid distributed by the UN Relief and Works Agency at the besieged al-Yarmouk camp, south of Damascus, Syria, on January 31, 2014. According to the UN Envoy for Syria, an estimated 400,000 Syrians have been killed since an uprising in March 2011 spiraled into civil war. See how the conflict has unfolded.