Theresa May is facing a furious backlash from MPs after she ordered UK forces to join the US and France in targeted airstrikes on Syrian chemical weapons facilities – without having gained the consent of parliament.

Hours after four RAF Tornado GR4 fighter jets launched Storm Shadow missiles at a military facility 15 miles west of Homs at 2am on Saturday, where the Assad regime is believed to stockpile the lethal weapons, the prime minister issued a passionate defence of the action, which she said had been taken for humanitarian reasons.

Having been briefed by military advisers at Downing Street after the strikes, May said that she was “confident” they had been successful.

A Downing Street spokesman said May spoke to President Macron and President Trump on Saturday afternoon and that they agreed the military strikes had been a success.

Play Video 2:05 What you need to know about the Syria strikes – video report

“The prime minister welcomed the public support which had been given by fellow world leaders for the strong stand the UK, France and the United States had taken in degrading Syria’s chemical weapons capability and deterring their use, defending global rules, and sending a clear message that the use of chemical weapons can never become normalised.”

Donald Trump struck a more triumphalist note. In a tweet he said: “A perfectly executed strike last night. Thank you to France and the United Kingdom for their wisdom and the power of their fine military. Could not have had a better result. Mission accomplished!”

But, while support came from fellow European leaders and much of the wider international community, Vladimir Putin condemned the action “in the most serious way”. The Russian president called an emergency meeting of the UN security council to address the crisis. As that meeting opened on Saturday night, amid talk in UN circles of a new cold war, the organisation’s secretary general, António Guterres, urged all security council members to show restraint and avoid further escalation. Nikki Haley, the US ambassador to the United Nations, told the meeting: “If the Syrian regime uses this poisonous gas again, the United States is locked and loaded.”

A Russian resolution at the UN security council condemning the air strikes met with a stinging diplomatic defeat. Moscow gained support from only two other countries, China and Bolivia. Four council members – Ethiopia, Kazakhstan, Peru and Equitorial Guinea - abstained, while the remaining eight members voted against. After the vote the Russian envoy, Vassily Nebenzia said “Today is a very sad day for the world, the UN, its charter, which was blatantly, blatantly violated.”

The strikes, which May maintained were “right and legal”, were ordered in response to the killing of 75 people, including children, in the Syrian town of Douma eight days ago. At a press conference early on Saturday May said the decision had been based on a mass of intelligence showing the Assad regime had been responsible for the Douma chemical weapons attacks.

But the prime minister came in for a barrage of criticism from opposition politicians at home. Labour leader Jeremy Corbyn accused her of “trailing after Donald Trump” and insisted that the prime minister should have sought parliamentary approval first.

Play Video 2:27 UK parliament should have been consulted on Syria strikes, says Jeremy Corbyn – video

“Bombs won’t save lives or bring about peace,” he said. “This legally questionable action risks escalating further, as US defence secretary James Mattis has admitted, an already devastating conflict and therefore makes real accountability for war crimes and use of chemical weapons less, not more, likely.”

Even Labour MPs who believed that action was necessary questioned why she had not waited until parliament returns on Monday to try to get its backing. Labour MP John Woodcock said: “It was right that the UK joined our allies in action to degrade Assad’s chemical weapon capability in Syria” but added that “the prime minister must explain to parliament why she believed it was not appropriate to put this to [a] vote in advance.”

Scottish first minister Nicola Sturgeon condemned the attacks and accused May of “complying with presidential wishes”, while Lib Dem leader Vince Cable warned: “Riding the coat-tails of an erratic US president is no substitute for a mandate from the House of Commons.” Caroline Lucas and Jonathan Bartley, the co-leaders of the Green party, said May had “trampled over parliamentary democracy” and called for a vote to be held on Monday.

May – who appeared to leave the door open to more strikes if the Assad regime repeated the used of chemical weapons – repeatedly dodged questions on whether she would seek some form of retrospective vote in parliament, saying only that she would address parliament on Monday, and take MPs’ questions.

At a Pentagon briefing Lt Gen Kenneth McKenzie said three targets had been struck in a “precise, overwhelming and effective” manner. One of these, the Barzah chemical weapons research and development centre near Damascus, was hit and “destroyed” by 76 missiles, 57 of them Tomahawks. “Initial indications are that we accomplished the military objectives without interference from Syria,” he said.

In the Syrian capital, Damascus, hundreds gathered to show their defiance in the face of western attacks, honking their car horns, flashing victory signs and waving Syrian flags after the airstrikes.

Some supporters of the anti-Assad opposition said they were disappointed that the strikes had been limited. “We had high hopes,” said Hussam, 40, who opposes the regime. “Unfortunately the only thing reverberating among us is disappointment. It wasn’t as intense as they’re making it sound. We have no more faith in the international community. Trump has been saying he will bomb for days now, like he’s warning Bashar ahead of time to be safe. If I am coming to murder someone, will I tell him beforehand? It’s ridiculous, it’s nonsense. They are laughing at us.”

Play Video 1:43 Theresa May: Syria strikes 'right and legal' option – video

May said the action, while specifically targeted at Assad, sent a wider message to others, including Russia, about the use of chemical weapons. Referring to the recent chemical weapons attack in Salisbury on former MI6 spy Sergei Skripal and his daughter Yulia she said: “We cannot allow the use of chemical weapons to become normalised – either within Syria, on the streets of the UK or elsewhere.”

Several European leaders rallied behind the joint UK, US and French action. German chancellor Angela Merkel said: “We support the fact that our UK and French allies took on responsibility in this way as permanent members of the UN security council. The military strike was necessary and appropriate in order to preserve the effectiveness of the international ban on the use of chemical weapons and to warn the Syrian regime against further violations.”