David Cameron: Mission against IS in Iraq will take "not just months but years
The UK Parliament has backed British participation in air strikes against Islamic State extremists in Iraq.
After a seven-hour debate, MPs voted for military action by 524 votes to 43.
The Conservatives, Lib Dems and Labour leaderships all backed air strikes although some MPs expressed concerns about where it would lead and the prospect of future engagement in Syria.
The BBC's political editor Nick Robinson said RAF planes could be called into action as early as Sunday.
Speaking after the vote, Defence Secretary Michael Fallon said a long campaign lay ahead and there would not be a "series of immediate hits".
He told the BBC the priority would be to stop the "slaughter of civilians" in Iraq and the UK and its allies would continue to be guided by Iraqi and Kurdish intelligence in identifying targets.
About 24 Labour MPs are thought to have voted against air strikes and a number of Conservatives abstained.
Earlier, Prime Minister David Cameron told MPs that intervention at the request of the Iraqi government was "morally justified" to combat a "brutal terrorist organisation" and was clearly lawful.
He won support from Labour leader Ed Miliband who said inaction would lead to "more killing" in Iraq, large swathes of which are controlled by Islamic State.
But shadow education minister Rushanara Ali, MP for Bethnal Green and Bow, resigned from the party's front bench in order to abstain in the vote.
In other developments:
Addressing MPs, Mr Cameron insisted Britain had a clear "duty" to join the campaign, saying IS was a direct threat to the UK and he was not prepared to "subcontract" the protection of British streets from terrorism to other countries' air forces.
Liberal Democrat leader Nick Clegg said it was "impossible to reason with" Islamic State and the UK should not be "paralysed" by the legacy of the 2003 Iraq War.
And Mr Miliband - who a year ago forced the prime minister to abandon plans for air strikes against the Syrian regime by inflicting a Commons revolt on the issue - said the UK "cannot simply stand by".
Speaking after the outcome of the vote, Labour MP John McDonnell - who voted against air strikes - said previous interventions in Iraq was one of the causes of the emergence of the jihadist movement.
"We seem to be making the same mistakes without any alternative strategy," he told BBC News.
The US began a series of air strikes in Iraq last month, and on Monday it began attacks on targets in Syria. Jets from Saudi Arabia and the United Arab Emirates have joined US forces in the attacks, and the US says more than 40 countries have offered to join the anti-IS coalition.
The government has said it would seek separate Parliamentary approval for the extension of air strikes to Syria but reserved the right to act without consulting MPs in the event of a humanitarian emergency.