Jaish al-Islam: 'Chemical attack' forced our fighters to abandon Douma

A high-ranking member of Jaish al-Islam said on Thursday that his group only agreed to abandon the besieged Eastern Ghouta town of Douma because of an alleged chemical attack by the Syrian regime.

"Of course, the chemical attack is what pushed us to agree" to a withdrawal from Douma, Yasser Dalwan, a high-ranking member of Jaish al-Islam, told AFP.

It was the first public acknowledgement by Jaish al-Islam of a deal reached for Douma, their last rebel holdout in the Eastern Ghouta suburb of Damascus.

The agreement was announced on Sunday morning by Syria's government and its ally Russia, just hours after toxic gases were allegedly released on Douma.

First responders there said more than 60 people died Saturday after suffering symptoms consistent with chemical exposure, including wheezing, discoloured skin and foaming at the mouth.

World powers have threatened a strong response, with French President Emmanuel Macron saying Thursday he had "proof" Syria's regime was behind the attack.

Syria and its ally Russia have both denied the accusations, and the global chemical watchdog said it would deploy a team to investigate.

Analysts have said Syrian President Bashar al-Assad may have used toxic gas to terrify Douma's residents and push rebels to withdraw without a fight.

Jaish al-Islam had long insisted that it would refuse to agree to an evacuation deal for Douma.

But since the alleged attack, several thousand rebels and civilians have left Douma for opposition-held territory in the north.

They included Jaish al-Islam's chief Issam Buwaydani, according to the Syrian Observatory for Human Rights, a Britain-based monitoring group.

"Not all the leadership has left yet. Departures are ongoing," Dalwan told AFP. 

Earlier, Syrian regime forces took full control over the besieged Damascus suburb of Eastern Ghouta, Russian officials said, raising the regime flag over the town of Douma.

A two month Russian-backed regime assault on the besieged Damascus suburb killed more than 1,700 civilians.