The global chemical weapons agency will investigate an alleged gas attack in Syria's Aleppo that reportedly wounded up to 100 people on Saturday, the agency's chief said on Monday.

Syria's regime has accused armed groups of carrying out a "toxic gas" attack that left dozens of people struggling to breathe and prompted government ally Russia to launch retaliatory air strikes on Sunday.

More than 100 buses headed early Wednesday to two towns in north-western Syria to evacuate thousands of people under a deal reached between an al-Qaeda-linked group and the Syrian government

International donors raised $4.4 billion in emergency aid for Syria and its neighbours on Wednesday, but the total fell well short of the UN target for 2018 after the United States failed to submit a pledge.

Syrian state television showed a convoy of pro-government fighters entering the Kurdish-held Afrin region on Tuesday to help fend off a Turkish assault.

At least 21 civilians, including five children, were killed on Monday in air strikes on Syria's northern Aleppo province, despite a "de-escalation zone" in place there, a monitor said.

Two tigers rescued from an abandoned zoo in the war-torn Syrian town of Aleppo are to be given a new home in a Dutch sanctuary, the animal refuge said Friday.

An international animal welfare charity was on Friday completing the evacuation of a dozen animals stranded in a neglected zoo in the conflict-torn Aleppo province of northern Syria.

Russia fought back Wednesday against what it called ‘fake news’ surrounding the battle for Aleppo, hosting a UN event with a video appearance by the boy whose blood-streaked face became a symbol of the conflict.

Islamic State attacked villages near the only useable road that links the government-controlled cities of Aleppo and Homs on Thursday, killing many residents, Syrian state media and a Britain-based war monitor said.

The evacuation of Syrian civilians and fighters from four besieged towns, part of a mediated swap deal between the warring sides, ended on Friday after a 48-hour halt, state media and a rebel official said.

Evacuations from four besieged areas of Syria resumed on Wednesday, Syrian state television, a Hezbollah media unit and a war monitor reported, days after a suicide bombing killed dozens in a convoy which was part of the same reciprocal agreement.