WHAT WE KNOW SO FAR:
- 129 dead, French prosecutor says, with 352 injured, 99 critically
- Locations targeted in suicide bombings and shootings
- 89 slain at Bataclan concert theatre after hostage situation
- Restaurants, football stadium attacked in night of horror
- Police leave cancelled and around 1,500 soldiers mobilised
- French border controls increased, state of emergency declared
- Seven extremists in three teams carried out attacks, all killed
- Manhunt under way for accomplices, arrests made in Brussels after police raids
- David Cameron chairs meeting of Government Cobra committee
- UK police say they will strengthen policing at ports and on the streets
One Briton has been confirmed killed in Friday's Paris terror attack that killed 129 and hundreds injured.
Nick Alexander is believed to have been working at the Bataclan theatre, where terrorists attacked a concert and took hostages, leaving 89 people dead.
The Foreign Office warned there could be a "handful" more British deaths in the shooting and bombing attacks, the worst violence in Paris since the Second World War.
In a statement, Mr Alexander's family said: "It is with huge sorrow that we can confirm that our beloved Nick lost his life at the Bataclan last night.
"Nick was not just our brother, son and uncle, he was everyone's best friend - generous, funny and fiercely loyal."
They added they took "great comfort in knowing how much he was cherished by friends throughout the world".
Mr Alexander is understood to have worked in merchandising for the band Eagles of Death Metal, who were playing at the Bataclan when the terrorists attacked.
Islamic State (IS) has claimed responsibility for the attacks, which were called "an act of war" by the French President Francois Hollande.
In response, British police said they would review their plans for how to deal with a similar incident in Britain and bolster policing at ports and on the streets.
"People may notice some changes at events at big cities across the country," Metropolitan Police Assistant Commissioner Mark Rowley, national lead for counter-terrorism, said.
"We will constantly keep that under review in the forthcoming days and weeks but we can't let the terrorists defeat us by becoming fearful and withdrawing from the streets. The term I would use is 'to be alert, not alarmed'."
French prosecutors have said the death toll could rise, adding that 352 people were injured and 99 of them remain in critical condition.
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Earlier, Downing Street said concerns remained about a "small number" of Britons who may have been caught up in the attacks, Downing Street said after David Cameron warned about the possibility of British casualties.
Officials confirmed the safety of many British citizens in Paris, but a team from the Metropolitan Police and extra consular staff were sent to work with the French authorities to establish the fate of other UK nationals in the French capital.
Speaking before any British deaths were confirmed, the Prime Minister warned that the UK should "be prepared for a number of British casualties" as he told the French people: "Your fight is our fight."
He said: "These were innocent victims enjoying a Friday night out with friends and family, no doubt at the end of a hard week.
"They were not seeking to harm anyone. They were simply going about their way of life – our way of life.
"And they were killed and injured by brutal, callous murderers who want to destroy everything our two countries stand for. Peace. Tolerance. Liberty. But we will not let them.
"We will redouble our efforts to wipe out this poisonous extremist ideology and, together with the French and our allies around the world, stand up for all we believe in."
Tower Bridge was among the world landmarks to be lit up in the colours of the French flag in a gesture of solidarity in the aftermath of the attack.
Tower Bridge lit up in the colours of the French flag on Saturday evening
A vigil was held in Trafalgar Square on Saturday afternoon and another, larger one is expected to be held there at 9pm.