Fifty-nine Tomahawk missiles targeted Shayrat airfield near Homs, Syria
President Trump said the attack was "in vital national security interest" of US
The action followed a suspected chemical weapons attack on civilians in a rebel-held town
The Syrian army says the strikes killed six and caused "extensive material damage"
Russia, a close Syrian ally, condemned the US "aggression" and suspended a joint air safety agreement
Today Programme
BBC Radio 4
Further use of chemical weapons by the Assad regime could result in a "much larger attack" by the US, a former vice chief of staff of the US Army, Jack Keane, told the Today programme.
From opposing military action to ordering strikes
Jeremy Bowen
BBC Middle East editor
The next step depends on whether the Americans regard this as a one-off, and so if there are no further chemical attacks will not do anything further.
One of the problems Western policy has had, since former President Barack Obama said he would take action and then didn't, has been a lack of credibility in the region. In Syria you get credibility by force.
When US Secretary of State Rex Tillerson said there was no future for Bashar Assad in Syria, I think that will be taken much more seriously in Damascus after this.
There's been a lot of talk about red lines - the Americans have always had a red line about not attacking the regime, now they've done it.
But President Trump has shown himself to be highly unpredictable. His administration has switched its view on Mr Assad in just a few days, so it's hard to predict what will happen next.
BBC foreign news producer Riam Dalati tweets:
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Today Programme
BBC Radio 4
James Jeffrey responds to the US missile attack on an air base in Syria
The US missile attack against an air base in Syria was "way overdue", the former US ambassador to Iraq James Jeffrey has told the Today programme.
President Donald Trump ordered the strike in response to a suspected chemical weapons attack on a rebel-held town.
No Russians were hurt in the missile strikes on the Shayrat Syrian airbase, Russian lawmaker Dmitry Sablin was quoted by Interfax news agency as saying. Mr Sablin, who is the deputy head of a Russian military veterans group, said the information was based on his own sources.
Turkey views US missile strikes against the Syrian air base positively and the international community should sustain its stance against the "barbarity" of the Syrian government, Turkish Deputy Prime Minister Numan Kurtulmus has told Turkish broadcaster Fox TV. President Bashar al-Assad must be fully punished in the international arena and the peace process in Syria needs to be accelerated, he also said.
The UK government says it "fully supports" the US missile strike against an air base in Syria in response to a suspected chemical weapons attack.
A No 10 spokeswoman said: "We believe [it] was an appropriate response to the barbaric chemical weapons attack launched by the Syrian regime, and is intended to deter further attacks."
Read our full news story here .
Today Programme
BBC Radio 4
Donald Trump has launched an air strike on Syria in response to a suspected gas attack
Retired air commodore with the RAF, Dai Whittingham, told the Today programme it's likely the Tomahawk missiles used were "1000lbs" worth of warhead. He said they were "long-range and extremely accurate".
BBC foreign news producer Riam Dalati has been tweeting messages he has received from a Syrian near the Shayrat airbase:
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Russian President Vladimir Putin's spokesman has described the US air strikes on the Shayrat airbase as an "aggression against a sovereign nation". Mr Putin sees them as an "attempt to distract the world from civilian casualties from US military action in Iraq," and they "do significant damage" to US-Russia ties", Dmitry Peskov said.
The governor of the Syrian city of Homs says the US attack caused civilian casualties in a village near the Shayrat airbase, Reuters cites the Lebanon-based al-Mayadeen TV station as reporting. He says five people were killed and seven injured in total by the strikes on the airbase.
Russians were present at the base the US struck on Thursday night but their role was not immediately known, CNN is quoting a US defense official as saying. And Reuters news agency is reporting that US officials said they informed Russian forces ahead of the missile attacks, and that there were no strikes on sections of the base where Russians were present.
"Iran strongly condemns any such unilateral strikes ... such measures will strengthen terrorists in Syria... and will complicate the situation in Syria and the region," the Iranian news agency ISNA quotes foreign ministry spokesman Bahram Qasemi as saying.
Konstantin Kosachev, chairman of the international affairs committee in the upper house of the Russian parliament, says the strikes were intended to "stamp an earlier verdict about [Syrian President Bashar] Assad's responsibility for a chemical attack in Idlib with gunpowder," the Interfax news agency reports.
The strike on the Shayrat airbase killed four Syrian soldiers and almost completely destroyed the facility, the UK-based monitoring group the Syrian Observatory for Human Rights says.
PJ Crowley, a former US assistant secretary of state, writes:
Fifty-nine cruise missiles are unlikely to change Assad’s no-holds-barred approach to the six-year-old Syrian civil war.
As Obama discovered after negotiating the removal of most (but evidently not all) of Syria’s chemical stocks in 2013, it still leaves the Assad regime free to use conventional weapons, and chlorine barrel bombs, to continue his assault on the so-called moderate Syrian opposition and civilians, backed fully by Russia and Iran.
Given that reality, Senators John McCain and Lindsay Graham have already encouraged the president to go further and take Syria’s air force “completely out of the fight”.
Obama feared just such a slippery slope. He chose to define America’s vital interest in Syria more narrowly, defeating the Islamic State without getting more deeply involved in another costly Middle East quagmire.
Ironically, until today, so did Trump, who opposed military action in 2013 and was elected to fix problems in America, not Syria. As he acknowledged, he is now responsible for the situation in Syria. But beyond appearing decisive, it’s doubtful he yet knows what to do about it.
Image source, White HouseThe questions that faced Obama in 2013 could now challenge Trump
Thursday's strike by the US could undermine the fight against terrorism, said Viktor Ozerov, the head of the defence and security committee at the Russian upper house of parliament.
He said Russia would call for an urgent meeting of the UN Security Council in response, Russia's state news agency RIA reported.
"This [strike] could be viewed as an act of aggression of the US against a UN nation," he said, according to the RIA report.
The Pentagon said Russian officials were warned in advance of the strike via a special conflict hotline.
At least 80 people were killed and hundreds injured in a suspected chemical attack on a rebel-held town in north-western Syria on Tuesday.
The symptoms of those wounded were consistent with reaction to a nerve agent.
Opposition groups and Western powers said a Syrian government air strike was responsible.
The Syrian military denied using any chemical agents. Its ally Russia said a rebel depot of chemical munitions was hit.
Children killed in Syria 'chemical attack'
Image source, ReutersA Tomahawk missile is launched from USS Porter
Here's a summary of the fast-moving US military action so far: