A meeting has been held at Russia's request

The head of the United Nations is warning of a "full-blown military escalation" in Syria.

Antonio Guterres has told a UN meeting, held at Russia's request, that all countries should "act responsibly in these dangerous circumstances".

Speaking before the gathering the US ambassador to the UN, Nikki Haley, said something will be done about Syria's apparent use of chemical weapons.

"Why do we think this is important? Because this is getting to be too normal.

"And this is something the United States, France, the UK and all of the international community is saying 'we can't absolutely have this'".

British Prime Minister Theresa May leaves Downing Street after attending a weekly cabinet meeting in London, UK | Image: NurPhoto/SIPA USA/PA Images

Yesterday the British Prime Minister Theresa May won the backing of her cabinet for action.

She spoke with US President Donald Trump last night - with both leaders agreeing that is "vital" that the use of chemical weapons does not go "unchallenged".

Over 70 people died and a further 500 were injured in the town of Douma near Damascus on Saturday.

The Syrian American Medical Society described patients foaming at the mouth and warned that victims had suffered corneal burns and smelled of a "chlorine-like odour."

Both Moscow and Damascus deny that the gas attack took place or that either regime was involved.