Syrian state media called the air strikes "a flagrant violation of international law".

The official Sana news agency cited an unnamed source as saying: "When terrorists failed, the USA, France and Britain intervened and committed aggression against Syria.

"The American, French and British aggression against Syria will fail."

Sana reported that the strikes hit a research centre north-east of Damascus, as well as other military facilities around the capital.

Missiles targeting military depots in Homs were intercepted, it said.

Writing on Twitter, external, Russian ambassador to the US Anatoly Antonov accused the Western powers of implementing a "pre-designed scenario".

"Again, we are being threatened. We warned that such actions will not be left without consequences," he added.

He accused US President Donald Trump of "insulting" his Russian counterpart, Vladimir Putin, in his televised address - something he called "unacceptable and inadmissible".

"The US - the possessor of the biggest arsenal of chemical weapons - has no moral right to blame other countries," he added.

Prime Minister Justin Trudeau said Canada condemned the "use of chemical weapons" and supported the US, UK and France.

According to the Canadian public broadcaster, CBC News, Mr Trudeau said Canada would continue to work with international partners and bring those responsible "to justice".

Within minutes of his announcement, President Trump was getting flak from both Republican and Democratic politicians for ordering the strikes without consulting the US Congress.

Democratic Senator Tim Kaine called it "reckless" and "illegal", and expressed concern the action might embolden Mr Trump to bomb Iran or North Korea.

And there was disquiet in the president's own party as Republican Congressman Thomas Massie called it unconstitutional.

Legal experts differ on the issue, and the debate raged a year ago when Mr Trump took similar action against Syria last April, external, following an attack on the rebel-held northern town of Khan Sheikhoun that UN and OPCW experts said involved the nerve agent Sarin.

The French presidency has tweeted a video which it says shows warplanes taking off before carrying out air strikes on Syria.

Russia has warned the US to expect the likelihood of some form of retaliation.

Its ambassador to the US, Anatoly Antonov, said in a statement "such actions will not be left without consequences".

One witness told the Reuters news agency that at least six loud explosions were heard in Damascus in the early hours of Saturday and that smoke was seen rising over the Syrian capital.

A second witness said the northern Barzah district had been hit.

Barzah is the location of a branch of the Scientific Studies and Research Centre (SSRC), a government agency.

A Western intelligence agency told the BBC last year that it believed chemical munitions were still being produced at the Barzeh facility, along with two other branches of the SSRC in the nearby Dummar district and in Masyaf, in Hama province.

Image source, Reuters

French President Emmanuel Macron said he had ordered the strikes on Syria because "dozens of men, women and children were massacred with chemical weapons".

"The red line had been crossed," he added.

The UK PM announces Britain's involvement in the strikes.

The UK Ministry of Defence (MoD) said four RAF Tornado jets were deployed to launch missiles at a Syrian military facility.

The former missile base was assessed to have been used by the Syrian regime to "keep chemical weapon precursors stockpiled in breach of Syria's obligations under the Chemical Weapons Convention", the MoD said in a statement.

Defence Secretary Gavin Williamson added: "The international community has responded decisively with legal and proportionate military force. Let these united actions send a clear message to the regime - the use of chemical weapons is categorically unacceptable and you will be held to account."

Image source, Getty Images

UK Prime Minister Theresa May has spoken for the first time since the announcement of the joint military action in Syria.

Mrs May said there was a need to , external"degrade the Syrian Regime’s chemical weapons capability and deter their use".

But she insisted: "This is not about intervening in a civil war. It is not about regime change."

Syrian opposition activists, rescue workers and medics say more than 40 people were killed last Saturday in a suspected chemical attack on Douma, which was the last rebel-held town in the Eastern Ghouta region near Damascus.

The Syria Civil Defence, whose rescuers are widely known as the White Helmets, and the Syrian American Medical Society, which supports hospitals in rebel-held areas, said victims were found with foam coming out of their mouths, blue skin and lips, and corneal burns.

France has said it has "proof" that "chemical weapons were used - at least chlorine - and that they were used by Bashar al-Assad's regime".

The Syrian government denies the allegation, and its key ally Russia says it has "irrefutable evidence" that the incident was "staged" with the help of the UK.

President Trump said the alleged chemical attack on Douma had not been carried out not by a man, but a "monster".

He appealed to those who were seen to be providing support to Syria's President Assad, including Russia and Iran, to think about who they stood by.

He described Russia as guilty of promoting "rogue states" adding: “What country wants to be associated with mass murder?”

Russia said on Friday that it had "irrefutable evidence" that the incident in Douma was "staged" with the help of the UK. The UK called the allegation "bizarre" and a "blatant lie".

In a televised address, President Trump said the strikes on what he called the Syrian government's "chemical weapons capabilities" would act as a deterrent.

The US, UK and France say they have launched missile strikes on Syrian government facilities in retaliation for a suspected chemical weapons attack on the town of Douma last Saturday.

US President Donald Trump said he had ordered strikes "on targets associated with the chemical weapons capabilities" of the Syrian government.

Explosions were reported near the Syrian capital Damascus.

The Syrian government insists it has never used chemical weapons and that the incident in Douma was fabricated.

Follow our live coverage for the latest updates.