RAF Tornado jets have carried out the first British bombing runs over Syria, the Ministry of Defence has confirmed.
The air strikes were carried out within hours of a vote by MPs in the Commons to back extending operations against Islamic State (IS) from neighbouring Iraq.
Four RAF Tornado jets, which carry a range of munitions including Paveway IV guided bombs and precision-guided Brimstone missiles, took off from the Akrotiri base in Cyprus, reportedly targeting an oil field in eastern Syria.
A Ministry of Defence spokesman said the sorties had returned from the "first offensive operation over Syria and have conducted strikes".
Prime Minister David Cameron has said MPs took the "right decision to keep the UK safe" after they overwhelmingly backed air strikes.
MPs voted by 397 to 223 last night in favour of extending British action to quash IS, also known as Isis, Isil and Daesh, from Iraq into its Syrian strongholds - a majority of 174.
Shadow foreign secretary Hilary Benn was lauded by MPs from across the House for making a powerful speech warning his party that "we never have and we never should walk by on the other side of the road".
He was among 66 Labour MPs who voted with the Government while seven Conservatives opposed the plans for military action.
Mr Cameron said: "I believe the House has taken the right decision to keep the UK safe - military action in Syria as one part of a broader strategy."
Foreign Secretary Philip Hammond said Britain was "safer" following the decision to back air strikes.
"We are very pleased that a significant number of Labour MPs have voted with the Government tonight so we have got a clear majority across the House of Commons in support of the action that we are now going to be taking to degrade this evil terrorist organisation, " he told Sky News.
"Britain is safer tonight because of the decision that the House of Commons has taken."
The vote has blown open deep divisions in the Labour Party with claims that MPs in favour of military action have faced threats of recriminations.
Leader Jeremy Corbyn's protests that the Government had failed to set out a convincing case did little to persuade a significant number of his parliamentary party, with 11 members of the shadow cabinet - including shadow foreign secretary Hilary Benn, deputy leader Tom Watson, shadow education secretary Lucy Powell, shadow health secretary Heidi Alexander and shadow Commons leader Chris Bryant - choosing to support Mr Cameron.
Pacifist Mr Corbyn was forced to offer his MPs a free vote and allowed Mr Benn to wrap up the debate arguing in favour of air strikes, in a messy compromise to stop the party from falling apart.
In astonishing scenes, the shadow foreign secretary gave an impassioned speech directly challenging his party leader, who sat beside him watching while MPs from across the House broke out into cheers of support.
Mr Benn told MPs Britain was under threat from fascists that held the country in contempt.
He added: "I say the threat is now and there are rarely, if ever, perfect circumstances in which to deploy military forces."
Mr Cameron opened more than 10 hours of debate in the Commons by warning that the "women-raping, Muslim-murdering, medieval monsters" of IS were "plotting to kill us and to radicalise our children right now".
Critics of the military intervention have disputed claims that 70,000 moderate fighters in Syria would be able to take on IS.
Tory chairman of the defence select committee Julian Lewis warned that "instead of having dodgy dossiers, we now have bogus battalions of moderate fighters".
US president Barack Obama welcomed the vote, describing IS as "a global threat that must be defeated by a global response".
The US-based SITE Intelligence Group, which monitors jihadist threats, said "Islamic State (IS) supporters on Twitter erupted in threats toward the UK and other Western countries" following the vote.