UK condemns chemical attack in Syria, says perpetrators must be held to account

London: Britain on Tuesday condemned a suspected chemical attack in Syria, saying it bore "all the hallmarks" of action by government forces and calling for those responsible to be "held to account".

"Horrific reports of chemical weapons attack in Idlib, Syria. Incident must be investigated and perpetrators held to account," Foreign Secretary Boris Johnson wrote on Twitter.

In a separate statement, he added: "This bears all the hallmarks of an attack by the regime, which has repeatedly used chemical weapons".

"If this is shown to be the work of the regime, it is further evidence of the atrocities perpetrated against the Syrian people over six years of appalling conflict," he said.

At least 58 people were killed and dozens left with breathing problems after the attack in the town of Khan Sheikhun, which also caused symptoms such as vomiting, fainting and foaming at the mouth, the Britain-based Syrian Observatory for Human Rights said.

France has called for an emergency meeting of the UN Security Council over the incident and the EU has said Syrian President Bashar al-Assad bears "primary responsibility" for the incident.

A senior Syrian security source, however, said that the attack was "a false accusation". Britain is co-hosting a Syria donors' conference in Brussels on Tuesday and Wednesday, and Johnson said he hoped it "steps up international assistance to the most vulnerable people affected by the conflict".

Syria agreed in a landmark 2013 deal to hand over its previously undeclared stock of chemical weapons for destruction by the Organisation for the Prohibition of Chemical Weapons (OPCW).

The Syrian government has repeatedly denied using chemical weapons in the civil war, which has killed 310,000 people since March 2011.