With images of women and children foaming from the mouth and nose circulating on social media, the death toll from Saturday evening’s attack on the town was said to have risen to at least 49, with some observers saying more than 150 people have been killed.
After condemning Iran and Russia’s Vladimir Putin for “backing animal Assad”, Donald Trump tweeted that there would be a “big price to pay” in connection with what he called a “mindless chemical attack” and an “atrocity”.
Earlier, one of the US president’s top homeland security advisers refused to rule out launching a missile strike in response to the alleged chemical weapons attack.
“I wouldn’t take anything off the table,” White House Homeland Security and Counterterrorism Adviser Thomas Bossert told ABC’s This Week. “We are looking into the attack at this point.”
Amid escalating tension on Sunday, the Russian foreign ministry issued a statement warning: “It is necessary to once again caution that military intervention under false and fabricated pretexts in Syria, where the Russian servicemen stay at the request of the legitimate government, is absolutely unacceptable and may trigger the gravest consequences.”
The ministry dismissed the Douma chemical attack allegations as “fake news to cover up terrorists and irreconcilable radical opposition, and to simultaneously try to justify potential external military strikes.”
Syrian state media, meanwhile, accused the rebels of trying to gain a military advantage by lying about the use of chemical weapons.
“[The] terrorists are in a state of collapse and their media outlets are [making] chemical attack fabrications in an exposed and failed attempt to obstruct advances by the Syrian Arab army,” state news agency SANA reported, citing an official source.
Amid claim and counter-claim, news agencies said it was impossible to independently verify what had happened in Douma, the last rebel-held town in eastern Ghouta, an area of Syria just outside the country’s capital Damascus.
But the Syrian American Medical Society (SAMS) and the ‘White Helmets’ Syria Civil Defence organisation, which operates in rebel-held areas, issued a joint statement claiming 49 people had died in the air attack.
SAMS said a chlorine bomb hit Douma hospital, killing six people.
Backing the Ghouta Media Centre’s claims, SAMS alleged that a second attack with “mixed agents”, including nerve agents, had hit a nearby building.
Basel Termanini, the US-based vice president of SAMS, said a further 35 people had been killed at a nearby apartment building, most of them women and children.
First responders said they found families suffocated in their homes and shelters with foam on their mouths. A White Helmets spokesman claimed rescuers were prevented from searching further by strong smells that made it hard for them to breathe.
One video circulated by activists showed the lifeless bodies of around a dozen children, women and men, some of them with foam at the mouth, along with the commentary: “Douma city, April 7 … there is a strong smell here.”
The joint SAMS and civil defence statement said medical centres had taken in more than 500 people suffering breathing difficulties, frothing from the mouth and smelling of chlorine.
At the same time Tawfik Chamaa, of the Union of Medical Care and Relief Organisations (UOSSM), a network of Syrian doctors, said 150 people were confirmed dead and the number was growing.
“The majority were civilians, women and children trapped in underground shelters,” he said.
Both the US State Department and the British Foreign Office reacted to the Douma allegations by issuing statements calling upon Vladimir Putin’s government to stop supporting the regime of Bashar al-Assad.
Mr Johnson, already in a war of words with Russia about the Novichok nerve agent poisoning of Yulia and Sergei Skripal in Salisbury, said: “Despite Russia’s promise in 2013 to ensure Syria would abandon all of its chemical weapons, international investigators mandated by the UN Security Council have found the Assad regime responsible for using poison gas in at least four separate attacks since 2014.
“These latest reports must be urgently investigated and the international community must respond. Russia must not yet again try to obstruct these investigations.”
Mr Johnson added: “Should it be confirmed that the [Syrian] regime has used chemical weapons again, it would be yet another appalling example of the Assad regime’s brutality and blatant disregard for both the Syrian people and its legal obligations not to use chemical weapons.
“It is truly horrific to think that many of the victims were reportedly families seeking refuge from airstrikes in underground shelters.
“Those responsible for the use of chemical weapons have lost all moral integrity and must be held to account.”
The Syrian rebel group Jaish al-Islam accused the Assad government of using chemical weapons, with a spokesman saying: “The Assad regime and its allies carry on with their crimes.”
A sceptical note, however, was struck by the Syrian Observatory for Human Rights.
The British-based monitoring organisation said at least 80 people had been killed, including around 40 who died from suffocation. But the organisation said the suffocations were the result of shelters collapsing on people inside.
If, however, it is independently confirmed that sarin was dropped on Douma, it would not be the first time the banned nerve agent has been used in Syria.
Declaring the incident a war crime, the commission reported: “Government forces continued the pattern of using chemical weapons against civilians in opposition-held areas.
“In the gravest incident, the Syrian air force used sarin in Khan Sheikhoun, Idlib, killing dozens, the majority of whom were women and children.”
At the time of the attack, doctors said victims started to choke, vomit and faint with foam coming out of their mouths. One pro-opposition witness reported finding entire families inside their homes, lying on the floor with their eyes wide open but unable to move.
When it reported in September 2017, the UN Commision of Inquiry said the Khan Sheikhoun incident was the worst of 33 chemical weapons attacks that it had documented.
The commission said 27 attacks were by Syrian government forces and the perpetrators of six other attacks had not yet been identified.
In August 2013, rockets containing sarin were fired at rebel-held areas of eastern Ghouta, but the UN mission that investigated this attack was not asked to determine if it was a government attack or a ‘false flag’ operation by the rebels.
The UN mission reported finding “clear and convincing evidence that chemical weapons were used against civilians, including children, on a relatively large scale in the Ghouta area on 21 August 2013.”
The UN mission’s 2013 report added: “Close to the rocket impact sites, in the area where patients were affected, the environment was found to be contaminated by sarin.”
Hundreds of people died in the attack.
The Assad government has repeatedly denied using chemical weapons. It explained the Khan Sheikhoun incident by saying its airstrikes had hit a chemical weapons depot belonging to rebel forces. This claim, however, was dismissed by the UN investigators.
The alleged chemical weapons attack on Douma comes after the Syrian government began a fierce air and ground assault on the town on Friday.
State TV showed thick clouds of smoke rising from Douma, where Jaish al-Islam is holding out after insurgents in other parts of eastern Ghouta accepted offers of safe passage to rebel-held areas in the north of the country.
Syrian state media accused Jaish al-Islam of killing six civilians in mortar bombardments of residential areas of Damascus on Saturday.
The rebel group, however, denied the accusation.
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