After six years of conflict in Syria, government backers Russia and Iran and rebel supporter Turkey have signed a deal to create four "de-escalation zones" in the country.

Syria accused Israel of triggering a huge explosion near Damascus airport on Thursday by firing several missiles at a military position.

Israel has carried out multiple air strikes in Syria since the country's civil war erupted in 2011, most of which it has said targeted arms convoys or warehouses of its Lebanese arch-foe Hizbullah, which is a close ally of the Syrian regime.

More than 3,000 Syrians are expected to be evacuated Sunday from four areas as part of a population transfer that was briefly stalled the day before by a deadly blast that killed scores of people, most of them residents of the besieged Shiite towns Foua and Kfarya.

France on Wednesday blasted Russia's vetoing of a U.N. draft resolution demanding the Syrian government cooperate with an investigation into a suspected chemical attack.

The U.N. Security Council is set to vote Wednesday on a resolution demanding that the Syrian government cooperate with an investigation of the suspected chemical attack in Idlib province, but Russia is likely to veto the measure, diplomats said. 

Israeli Defense Minister Avigdor Lieberman said Thursday he was "100 percent sure" Syrian President Bashar al-Assad ordered a suspected chemical attack this week that provoked international outrage.

Lieberman said the alleged attack in the neighbouring country was carried out "on the direct and premeditated command of Syrian President Bashar al-Assad with Syrian planes."

Syria's armed forces "did not and will not" use chemical weapons, even against jihadist groups, Foreign Minister Walid Muallem said on Thursday. 

"I stress to you once again: the Syrian army has not, did not and will not use this kind of weapons -- not just against our own people, but even against the terrorists that attack our civilians with their mortar rounds," he said. 

French President Francois Hollande on Wednesday called for an international response to the suspected chemical attack that killed scores of civilians in Syria, calling it a "war crime."

All evidence points to Syrian President Bashar al-Assad being behind a suspected chemical weapons attack which left more than 70 dead in a rebel-held town, British Foreign Secretary Boris Johnson said Wednesday. 

The EU and U.N. on Wednesday rallied donor countries and aid groups to support a devastated Syria at a conference overshadowed by a suspected chemical attack blamed by the West on Damascus.