Jaish al-Islam, the last remaining rebel group in Eastern Ghouta, has agreed to leave its holdout in Douma for an opposition-held area in northern Syria, according to opposition negotiators and the Russian foreign ministry.

The deal came a day after a chemical attack killed scores of people and affected hundreds of other Douma residents. The attack prompted global outrage but was dismissed as “fabrication” by the Syrian government, whose forces on Friday launched an offensive against the rebels under the cover of air raids.

The agreement, which was reached between Jaish al-Islam and Russia on Sunday, includes a ceasefire and the evacuation of fighters and civilians from the area.

“According to people who helped negotiate this agreement, Jaish al-Islam has agreed with the Russian forces to begin evacuating with their families, as well as anyone else who wants to leave,” Al Jazeera’s Natasha Ghoneim, reporting from Amman, said.

Under the agreement, Russian military police will move into Douma to keep Syrian forces out, added Ghoneim.

The Russian army also said on Sunday it had struck a deal with Jaish al-Islam to withdraw about 8,000 of its fighters and some 40,000 of their relatives.

Major General Yuri Yevtushenko was quoted as saying by The Associated Press news agency that a convoy of 100 buses had entered Douma to begin the evacuation.

Russian news agency RIA, citing a security source, said Jaish al-Islam fighters  will leave Douma in two batches in the coming hours.

A deal was also reported earlier in the day by Syria’s official news agency SANA, which cited a government source as saying that the agreement would see “the departure of all so-called Jaish al-Islam terrorists to Jarablus within 48 hours”.

In exchange, Jaish al-Islam would release hostages it had been holding, the source said, according to SANA.