The UK's opposition leader, Jeremy Corbyn, said the decision to launch an attack on Syria was a "legally questionable action".

He said Prime Minister Theresa May should have sought parliamentary approval instead of taking instructions from Washington.

UK Defence Secretary Gavin Williamson has described British air strikes on a Syrian target as "highly successful" and said the crews of the four fighter jets involved had returned safely.

Speaking to the BBC, he said: "Every early indication is that it has been a highly successful mission... Our service personnel have played an important role in terms of degrading the ability of the Syrian regime to use chemical weapons in future."

Here is our latest map showing locations in Syria where Western air strikes are believed to have taken place.

Earlier, US and French officials said three targets had been struck:

• A scientific research facility in Damascus, allegedly connected to the production of chemical and biological weapons
• A chemical weapons storage facility west of Homs
• A chemical weapons equipment storage site and an important command post, also near Homs

However, the Reuters news agency cited a pro-Assad militia commander as saying that air strikes had taken place in several other locations.

And the Russian government said missiles targeting a military airfield eats of Damascus had been intercepted.

Iran's supreme leader, Ayatollah Ali Khamenei, has said that the Western attack on Syria is a crime that will have no gain.

In a speech cited by Iranian TV, he said: "US allies will not gain any achievement from crimes in Syria. Attacking Syria is a crime.

"The US president, UK prime minister and the president of France are criminals."

Iran is a staunch ally of President Bashar al-Assad and is believed to have deployed troops and spent billions of dollars to help the Syrian government.

Double the firepower with new allies - but is it enough to stop Assad's chemical weapon use?

Image source, Google

Russia's defence ministry says Syrian air defence systems intercepted 12 missiles fired at a Syrian military airfield east of the capital Damascus.

"The Syrian military airfield Dumayr located east of Damascus was attacked with 12 cruise missiles. The Syrian armed forces' air defence intercepted all of the cruise missiles," the Russian Defence Ministry said, Interfax news agency reported.

The BBC's Middle East Correspondent Kevin Connolly says it is a carefully calibrated statement designed to suggest that a key target for the attacks - the aircraft and crews accused of launching chemical weapons in Douma last week - may have escaped unscathed. No evidence has been provided to back up the claim.

Russian officials had earlier said that a number of the missiles fired by the US, UK and France had been intercepted.

The former US ambassador to the UN, Samantha Power, has said that Western military strikes on suspected chemical weapons sites in Syria are appropriate because Russia can block action through the United Nations using its veto.

"Russia would never allow any meaningful response through the UN Security Council," she said in a series of tweets.

Ms Power added that unilateral US sanctions would not be enough to deter the Syrian government.

But she questioned President Trump's overall policy on Syria.

"Can anyone on earth define US policy toward Syria? Since Trump took office, there hasn’t been a single serious, sustained diplomatic initiative aimed at ending the war," she said.

The Turkish foreign ministry has said in a statement that it welcomed the strikes against President Bashar al-Assad's regime, calling it an "appropriate response".

The attack launched by Britain, the US and France "has eased humanity's conscience in the face of the attack in Douma", it said.

The suspected chemical weapon attack against civilians in Douma last week constituted "crimes against humanity" that should not go unpunished, added Ankara.

The Syrian government has said the incident was fabricated, while its ally Russia has said it was staged with the help of the UK.

Turkey has supported rebels fighting the Syrian government, but has also launched an offensive against Kurdish forces in northern Syria and has reportedly struck a deal with Russia - a key Syrian government ally - to use its air power in northern Syria.

The European Council president Donald Tusk has responded to the launch of airstrikes on Saturday morning via Twitter, saying:

"Strikes by US, France and UK make it clear that Syrian regime together with Russia & Iran cannot continue this human tragedy, at least not without cost."

Jonathan Beale
BBC defence correspondent

Image source, PA

The four British Tornado Jets took off in the early hours of this morning here from RAF Akrotiri in Cyprus.

Each was armed with a Storm Shadow missile. The cruise missile is 5m (16ft) long and has a range of 300 miles (480 km). They had already been programmed to find their target using GPS.

The four Tornados fired the missiles well away from Syrian airspace out of range of the regime's air defences and then they all returned safely.

The Ministry of Defence has described the action as "proportionate".

While the UK might appear to have played a minor role in these strikes the defence secretary Gavin Williamson said it was part of a united response that sent a clear message to President Assad.

Image source, PA

This attack was more significant than the US strike against a Syrian air base a little over a year ago, but at first sight seems more limited than President Trump's rhetoric may have suggested.

Last year some 59 missiles were fired. This time a little over double that number were used.

The strikes are over for now, but there was a clear warning that if the Assad regime resorts to chemical weapons again then further strikes may well follow.

Care was taken, say the Americans, to avoid both Syrian and "foreign" - for that read Russian - casualties.

But the fundamental questions remain. Will President Assad be deterred?

Last year's US strike failed to change his behaviour. This time, will it be any different?

Image source, MoD

The Ministry of Defence said Storm Shadow missiles were launched by four RAF Tornados at a former missile base 15 miles (24 km) west of Homs, where it is thought the Assad regime has been stockpiling items used to make chemical weapons.

A spokesperson added the facility was "located some distance from any known concentrations of civilian habitation" and scientific analysis was used to "minimise any risks of contamination to the surrounding area".

The Iran-backed Lebanese militant group Hezbollah - thousands of whose fighters are supporting the Syrian military in the civil war - has condemned the US-led missile strikes.

"The war that America is waging against Syria, against peoples of the region and resistance and liberation movements, will not realise its goals," a statement said.

The Syrian presidency has tweeted a short video of Bashar al-Assad walking into his office at 09:00 local time (06:00 GMT) with the caption: "Morning of steadfastness."

The message appears to be that the Syrian government has been unaffected by the Western air strikes targeting its facilities.

A Syrian foreign ministry source has denounced the Western strikes as a "brutal, barbaric aggression".

The official Sana news agency cited the source as saying the strikes were intended to derail an investigation by the Organisation for the Prevention of Chemical Weapons (OPCW) into the suspected chemical weapons attack in Douma last Saturday.

Members of an OPCW fact-finding mission were expected to visit Douma, which was the last rebel-held town in the Eastern Ghouta region outside Damascus, later on Saturday.

The foreign ministry source said the strikes were aimed at "hindering the mission's work and pre-empting its results".

France has said it has "proof" that chemical weapons were used by the Syrian government. The government has denied the allegation.

What we know about Douma 'chemical attack'

BBC Monitoring
The world through its media

Image source, AFP

The Russian defence ministry says the Syrian military used decades-old hardware to counter the US-led missile strike.

"Syrian air defence systems S-125, S-200, Buk and Kvadrat were used in repelling the missile strike. These air defence systems were manufactured more than 30 years ago in the Soviet Union," the Russian defence ministry said in a statement reported by Interfax news agency.

Russia's state-of-the-art air defence system was "not used to repel the missile strike", according to the ministry.

The Russian air defences have been set up around the port of Tartous and the Hmeimim air base near the Mediterranean coast, which are both used by Russia, the ministry said.

Image source, AFP

The Reuters news agency cites a pro-Assad militia commander as saying that in addition to the research centre in Barzeh and the arms depot in Homs, the following locations were hit:

• A military base in the Dimas area, external, near the Lebanese border west of the Damascus. Israeli warplanes were reported to have bombed an airport in the same area in 2014, external.
• A site in Masyaf, external, in Hama province north of the capital. Masyaf is reportedly the site of a branch of the Scientific Studies and Research Centre (SSRC) that Western intelligence agency said last year was producing chemical munitions.
• Army depots in the eastern Qalamoun region, external, north-east of Damascus
• The Kiswah area, external, south of Damascus. Iran is believed to have been building a permanent military base outside Kiswah. In December, Israel is reported to have fired missiles at the facility and destroyed several buildings, external.
• A site in the Qasyoun hills, external, overlooking Damascus

Image source, Reuters

French ministers have been giving details about their country's role in the co-ordinated missile strikes on Syria.

Foreign Minister Jean-Yves Le Drian said the strikes were "legitimate", "proportionate" and "targeted".

Defence Minister Florence Parly said a French navy frigate in the Mediterranean and warplanes flying from bases in France targeted the main chemical weapons research centre in Syria, as well as two major chemical weapons production sites.

But Ms Parly said France was not looking for confrontation and did not want military escalation.

She also said that Russia had been warned in advance of the strikes.

Earlier, US General Joseph Dunford said Russian forces in Syria had been warned through existing "deconfliction" channels that Western planes would be entering Syrian airspace, but without revealing the target sites or timing in advance.

UK Foreign Secretary Boris Johnson has welcomed British involvement in the action, external against Syria.

"The world is united in its disgust for any use of chemical weapons, but especially against civilians."