Macron condemns Syria 'chemical attacks': Elysee

French President Emmanuel Macron accused Damascus of "chemical attacks" against civilians in the Syrian rebel enclave of Douma in a call with US leader Donald Trump today, as international outrage mounts against the alleged use of the weapons.

The statement from the Elysee Palace said Macron "strongly condemned the chemical attacks on April 7 against the population of Douma".

It added that the two leaders shared information "confirming" the use of chemical weapons and would coordinate their efforts at a meeting of the UN Security Council in New York later today.

Trump has warned there would be a "big price to pay" after Saturday's attack, as rebels began evacuating Douma, the last sliver they held of their one-time stronghold Eastern Ghouta, under a deal with Syria's regime.

"Many dead, including women and children, in mindless CHEMICAL attack in Syria," Trump wrote on Twitter, lashing out at Syrian President Bashar al-Assad and Russia's Vladimir Putin, a key ally of the regime.

Damascus and its allies have denounced the accusations.

Syria's White Helmets, who act as first responders in rebel-held areas of Syria, said "poisonous chlorine gas" had been used yesterday.

In a joint statement with the Syrian American Medical Society, the White Helmets said more than 500 cases were brought to medical centres "with symptoms indicative of exposure to a chemical agent".

France, which has repeatedly said evidence of chemical use in Syria could prompt military action, responded by calling for an urgent UN Security Council meeting on today.

The request was also signed by eight other UN Security Council members including the US and Britain, while Russia asked for a separate Security Council meeting to discuss global threats to peace.