France's Macron vows 'immediate retaliation' to Syria chemical attacks

France will respond immediately to any use of chemical weapons in Syria, France's president has said, in a threat likely directed at the regime of Syrian President Bashar al-Assad. 

Emmanuel Macron gave the warning on Monday during "frank talks" at Versailles palace with his Russian counterpart Vladimir Putin, who is a staunch ally of Assad.

"There is a very clear red line for us, which is the use of the chemical weapons by whichever party," Macron said at a joint news conference with Putin.

"Any use of chemical weapons will mean an immediate relation at least on the part of French forces," he added.

He did not specify the form of such reprisals, but France flies warplanes over Syria and Iraq, striking Islamic State group targets as part of an international coalition.

France has published evidence that the Assad regime was responsible for the April 4 chemical attack in Khan Sheikhoun, which killed at least 88 people.

Following the sarin gas attack, the US launched a barrage of missiles at the regime's Shayrat airbase, which it said was the launchpad for the attack.

The newly elected French leader also said on Monday that he wanted to work more closely with Russia to try to resolve the six-year war in Syria, one of the sticking points in relations between the West and Moscow.

Calling for "a democratic transition that preserves the Syrian state," he warned that "failed states" in the Middle East emboldened terror groups and posed a threat to the West.

Progress in Syria "will happen by a joint effort, which today we laid the foundations for," Macron said.

"We disagree on a number of things but at least we discussed them," Macron said.

"Our absolute priority is the fight against terrorism and the eradication of terrorist groups and Daesh in particular," he said, using an alternate name for IS, which has claimed several deadly attacks in France.

Monday's visit came seven months after the Russian leader cancelled a trip to Paris amid a row over Syria with Macron's predecessor Francois Hollande, who had said Russia's bombing of Aleppo could amount to war crimes.