The British parliament has approved authorisation to use military force against the Islamic State of Iraq and the Levant (ISIL) group in Syria, despite sharp objections and a warning of an "ill thought-out rush to war" from the opposition Labour Party.
The vote on Wednesday followed more than 10 hours of debate, with David Cameron, the UK prime minister, calling on Britain to take immedate action against the "medieval monsters" in its stronghold within Syria.
For his part, the opposition Labour Pary leader, Jeremy Corbyn, questioning the lack of strategy to defeat ISIL and end the civil conflict.
A total of 397 MPs voted in favour of the air strikes, while 223 voted against.
"These terrorists are plotting to kill us and to radicalise our children right now," Cameron said.
Related: Syrians in UK plead for a vote against air strikes
"The question is this: do we work with our allies to degrade and destroy this threat and do we go after these terrorists in their heartlands?" he said.
"Or do we sit back and wait for them to attack us?"
But Corbyn said Cameron's arguments for an immediate strike "simply do not stack up" as it puts "emphasis on bombing now."
"In my view only a negotiated political and diplomatic endeavour to bring about an end to the civil war in Syria will bring some hope to the millions" of refugees, he said, while questioning whether the bombings could reduce or increase the threat to Britain.
With the vote, Britain's bombing against ISIL in Iraq will expand to Syria within days, or even hours.
'Head of the snake'
Referring to the attacks in France that killed 130 people last month, Cameron urged his country to "answer the call" from its allies and take part in the air strikes.
"We should answer the call from our allies. The action we propose is legal, it is necessary and it is the right thing to do to keep our country safe," he said.
He said what happened in Paris showed "the extent of terror planning from [ISIL]. This was, if you like, the head of the snake in Raqqa in action."
Several Conservative MPs voted against the proposal and Cameron had to rely on Labour MPs breaking ranks with their leader Corbyn to approve the move.
Cameron defended his action, saying that the military action was only "one part of the answer" in resolving the crisis.
"I am not pretending that the answers are simple, the situation in Syria is incredibly complex," he said, dismissing criticisms that it would be a repeat of the decision to go to war in Iraq.
He also argued that Britain could "make a real difference" in the conflict because of its precision targeting, particularly with Brimstone missiles.
Al Jazeera's Emma Hayward, reporting from London, described the debate as a "rowdy" and "lively one".
Still, she said, there was a sense of "inevitability" that the proposal would pass despite a divided public opinion, with less than half supporting it.
In an interview with Al Jazeera, Richard Dannatt, former UK army general, said extending the operation to Syria from Iraq is only a "small element" in the strategy against ISIL.
"Over and above that, we've got to put all that we are doing into a wider diplomatic and political framework to build a more secure for Syria, and to secure the region itself.," he said.
Source: Al Jazeera and agencies