Syrian opposition activists, rescue workers and medics say more than 40 people were killed on 7 April in a suspected chemical attack on Douma, which was the last rebel-held town in the Eastern Ghouta region.
France has said it has “proof” that “chemical weapons were used – at least chlorine – and that they were used by Bashar al-Assad’s regime”.
The Syrian government denies the allegation, and its key ally Russia says it has “irrefutable evidence” that the incident was “staged” with the help of the UK.
Why was Douma being bombed?
In February, forces loyal to President Bashar al-Assad launched an assault on the Eastern Ghouta that has reportedly left more than 1,700 civilians dead.
In March, troops split the region into three pockets – the largest of which was around Douma, home to between 80,000 and 150,000 people. Facing defeat, rebel groups in the other two pockets agreed to be evacuated to northern Syria.
But the group controlling Douma, Jaysh al-Islam, continued to hold out. On 6 April, after negotiations with the government stalled, air strikes resumed.
What happened on 7 April?
The bombardment continued for a second day, with dozens of people reportedly killed or injured by conventional munitions before the suspected chemical attack.
Activists from the Violations Documentation Center (VDC), which records alleged violations of international law in Syria, reported two separate incidents of bombs believed to contain toxic substances being dropped by the Syrian Air Force.