Theresa May 'no practicable alternative' to bombing Syria: Read her full statement

President Donald Trump says the United States, France and Britain have launched military strikes in Syria to punish President Bashar Assad for an apparent chemical attack against civilians and to deter him from doing it again.

The US and its allies, including the United Kingdom, are now considering whether to strike Syria over a suspected poison gas attack that medical relief organisations say killed dozens of people in the rebel-held town of Douma near Damascus on Saturday. The opposition does not have helicopters or use barrel bombs.

"We can not risk an escalation even further than it's gone already", he added.

"Theresa May should have sought parliamentary approval, not trailed after Donald Trump".

Meanwhile, the idea of an intervention gained more momentum in the United Kingdom on Thursday, after Brexit Secretary David Davis hinted he had changed his mind since voting against Syrian intervention under similar pretexts in 2013.

Stop the War, a pacifist coalition once chaired by Corbyn, has called a demonstration outside the British parliament on Monday to protest about the strikes.

Mrs May is still yet to unequivocally point the finger of blame at the Assad government but she has spoken of the need for action "if" the regime is found to bear responsibility.

British media said that ministers are expected to back May's call to join the threatened military action.

Mrs May said chemical weapons had "all too often" been used in recent times.

However, some of her MPs have expressed caution about getting involved in the complex conflict in Syria and are pressing for parliament to be recalled from its Easter break to discuss any action.

'This is the first time as Prime Minister that I have had to take the decision to commit our armed forces in combat - and it is not a decision I have taken lightly.

But after the Conservatives entered office in 2010, the government suggested that since the 2003 vote on Iraq, a convention had emerged that MPs should have a say, except in cases of emergency.

Mr Trump said the Syrian regime's use of chemical weapons on Douma was a "significant escalation in a pattern of chemical weapons use by that very awful regime".

Other strikes targeted an army depot near Homs.

Mrs May has described the alleged use of chemical weapons as a "humanitarian catastrophe" that "cannot go unchallenged".

Vince Cable, leader of the Liberal Democrats, the fourth-biggest party in parliament, accused May of "riding the coat-tails of an erratic U.S. president".

Shahnaz, calling into LBC, said: "Why would Britain contribute to this war?"

DUP leader Arlene Foster said the airstrikes were "limited but proportionate and justified".

"Corbyn will rail against military action, claiming it could widen the conflict, but if he won't sanction military action against a regime that is using chemical weapons on its own people, when would he ever sanction it?" he told AFP.

Brexit Secretary David Davis, who voted against military action in 2013, said "we've got to make this judgment on a very careful, very deliberate, very well thought-through basis, knowing exactly ... how strong the evidence is".

Former Prime Minister Tony Blair on the other hand defends such a military move without parliamentary consent.