In an address, Mr Trump said the attack had been undertaken "to establish a strong deterrent against the production, spread and use of chemical weapons". But he added: "We are prepared to sustain this response until the Syrian regime stops its use of prohibited chemical agents." He said the actions of Syrian President Bashar al-Assad were not the work of a man, but the "crimes of a monster instead". British Prime Minister Theresa May said: "This is not about intervening in a civil war. It is not about regime change. It is about a limited and targeted strike that does not further escalate tensions in the region and that does everything possible to prevent civilian casualties." She said Russia had used its veto power in the United Nations Security Council to prevent a proper international investigation of the use of chemical weapons by the Syrian regime in its ongoing civil war.

President Donald Trump has launched air strikes against Syria. Credit:AP The attack was supported by other US allies, including Canada and Australia. Australian Prime Minister Malcolm Turnbull described the strike as a "calibrated, proportionate and targeted response". "The use of chemical weapons by anyone, anywhere, under any circumstances is illegal and utterly reprehensible," Mr Turnbull said. "The Assad regime must not be allowed to commit such crimes with impunity." About 120 missiles targeted three main sites: a research centre near Damascus; a storage facility near Homs, thought to be the "primary location" of Syrian sarin gas; and a nearby storage facility that also served as a command post. Loading

The strikes have raised global fears of possible conflict between Russia, a key ally of Syria, and the US. Just a week earlier, Trump had shocked his own security chiefs by abruptly announcing his intention to rapidly remove US troops from Syria, where they have been fighting IS militants. In a statement, Russian ambassador to the US Anatoly Antonov said of the attack: "A pre-designed scenario is being implemented. "Again, we are being threatened. We warned that such actions will not be left without consequences. All responsibility for them rests with Washington, London and Paris." A senior Russian official in Damascus, Dmitry Sablin, told the Russian news outlet Tass that he believed the strike was designed to interfere with investigations that had already begun into the chemical attack. He advised "the Western adventurists who have unleashed aggression in the Middle East again to turn an attentive ear to the warning from the chief of Russia’s General Staff Valery Gerasimov such aggression would not remain unretaliated."

In April last year, Trump ordered another, more limited missile strike, against an airfield in Syria from which an earlier chemical attack had been launched, according to US intelligence. The Syrian regime acknowledged it held a stockpile of chemical weapons that are banned under international law though, since then, it has denied using them. The Independent International Commission of Inquiry on the Syrian Arab Republic says it has confirmed at least 34 chemical attacks since 2013, many of which it said used chlorine or sarin, a nerve agent, The New York Times has reported. All but six were confirmed to have been conducted by the Syrian government. The commission, which is investigating the attack on Douma, is an independent body established by the UN Human Rights Council to investigate human rights violations in Syria. The strikes come as Mr Trump faces a domestic crisis at home as investigations continue into whether his campaign colluded with Russian meddling in the US election on his behalf or has sought to obstruct justice since.