The US has called on Russia to end its support for the Syrian regime after at least 70 people were killed in an alleged chemical attack.
The State Department in Washington said it was closely following the “disturbing reports” from the city of Douma in eastern Ghouta, which an aid group with links to opposition forces in the region said had been subjected to “one of the worst chemical attacks in Syrian history” late on Saturday.
As well as the dead, more than 500 other civilians were injured in the strike, the Union of Medical Care and Relief Organisations (UOSSM) told Sky News.
The Syrian American Medical Society described patients foaming at the mouth, with corneal burns, finding it difficult to breathe and smelling of a “chlorine-like odour”. One woman had convulsions and pinpoint pupils.
“The reported symptoms indicate that the victims suffocated from the exposure to toxic chemicals, most likely an organophosphate element,” it said.
The medical relief group also claimed an “explosive barrel” attack on Douma hospital and its surrounding area had prevented ambulances from reaching victims.
It has demanded “an immediate cease-fire in the city of Douma and the entry of international investigation teams from the Organisation for the Prohibition of Chemical Weapons (OPCW) to investigate this heinous chemical attack”.
There has been no independent verification of the allegations of a chlorine gas attack – which have been denied by the Syrian government and Russia.
The alleged strike has triggered widespread alarm with Britain and the US calling for an “immediate response by the international community” if the claims are proven.
“These are very concerning reports of a chemical weapons attack with significant number of casualties, which if correct, are further proof of Assad’s brutality against innocent civilians and his backers’ callous disregard for international norms,” the Foreign Office said.
“An urgent investigation is needed and the international community must respond. We call on the Assad regime and its backers, Russia and Iran, to stop the violence against innocent civilians,” it added.
“The United States continues to use all efforts available to hold those who use chemical weapons, in Syria and otherwise, accountable,” the State Department said in a statement, which referenced the deadly sarin gas attack by the Assad regime on the town of Khan Sheikhoun last year.
In a further sign of tensions between Moscow and the West, it added: “The Assad regime and its backers must be held accountable and any further attacks prevented immediately.
“Russia, with its unwavering support for the regime, ultimately bears responsibility for these brutal attacks, targeting of countless civilians, and the suffocation of Syria’s most vulnerable communities with chemical weapons.”
The statement went on to accuse Russia of breaching its commitments to the United Nations and the Chemical Weapons Convention, and said it must withdraw its support for Mr Assad to prevent “further, barbaric chemical weapons attacks”.
Volunteer rescue service The White Helmets, which also has links to anti-Assad forces, said many of the victims of the alleged attack were women and children.
The group published photos showing a number of dead children appearing to be frothing at the mouth.
Reuters and Getty also released pictures showing the aftermath of what both news agencies described as a “poisonous gas attack” by the Syrian regime, including a number of dead youngsters.
Other children, including crying babies, were shown in deep distress and receiving medical treatment.
The UK-based Syrian Observatory for Human Rights reported 11 cases of symptoms of suffocation in the besieged city, including five children, but has not said what agents may have been used or whether there had been any deaths.
Syrian state media said rebels in Douma were in a state of collapse and making “chemical attack fabrications”.
The Syrian government has recaptured nearly all of eastern Ghouta from rebels in an offensive that began in February, leaving just Douma in the hands of insurgent group Jaish al Islam.
Last year, a joint inquiry by the UN and the Organisation for the Prohibition of Chemical Weapons found the Syrian government was responsible for the sarin attack in April 2017.
The inquiry had previously found that Syrian government forces were responsible for three chlorine gas attacks in 2014 and 2015, and that Islamic State militants had used mustard gas.