Syria civil war: 'Dozens of civilians killed in chemical weapons attack' on Douma in eastern Ghouta, says monitor

US State Department says it is monitoring the situation and that Russia should be blamed if chemicals were used

Dozens of civilians have reportedly been killed after the Syrian government dropped a barrel bomb containing a chemical weapon in eastern Ghouta.

At least 25 people were killed and more than 500 injured after the attack in Douma, according to the Union of Medical Care and Relief Organisations.

The Paris-based aid agency, known by its French initialism UOSSM, said many of the victims were children.

The White Helmets rescue organisation said 40 people, mostly women and children, had been killed.

It said hundreds were being treated at medical centres.

Syrian state media denied government forces had launched any chemical attack as soon as the reports began circulating and said rebels in the eastern Ghouta town of Douma were in a state of collapse and spreading false news.

On Saturday evening, the US State Department said it was monitoring the situation and that Russia should be blamed if chemicals were used.

Images on social media appeared to show families, mostly women and children, foaming at from the mouth and nose.

Syrian rebel group Jaish al-Islam blamed the government for the attack, which it said injured more than 500 people.

"The Assad regime and its allies carry on with their crimes," the rebels' military spokesman, Hamza Birqdar, told al-Hadath TV.

The Syrian Observatory for Human Rights, a Britain-based war monitor, reported 11 cases of symptoms of suffocation in the city, including five children, following strikes by Syrian warplanes.

It did not say what agents may have been used in the attacks.

Neither the rebel group nor the Observatory mentioned any deaths.

Syrian state media denied launching chemical attacks as soon as the reports began circulating.

"Jaish al-Islam 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.

On Friday, the government launched a fierce air and ground assault on Douma, the last rebel-held town in eastern Ghouta, killing 48 people in the last 24 hours alone.

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.

Six civilians were killed on Saturday in mortar shelling of residential neighbourhoods of the capital Damascus, and 38 others were injured, Syrian state media reported, accusing Jaish al-Islam of the attacks. The rebel group's spokesman issued a statement denying the accusation.