Islamic State has claimed responsibility for a series of coordinated attacks across Paris that has left at least 127 dead, in what the French president described as "an act of war".
In an online statement, the group said it had carried out the shootings and suicide bombings at restaurants, a concert hall and a football stadium that led to a state of national emergency and boosted border controls.
A Syrian passport has been found on the body of a suicide bomber at the Stade de France stadium in Paris, police officials have said.
One bomber was a young Frenchman flagged for links with Islamic extremism, they said.
Francois Hollande denounced the terror attacks, which saw shootings and suicide attacks across the French capital, and declared three days of national mourning.
The Eiffel Tower has been closed indefinitely according to the attraction's management.
Journalist Julien Pearce, who was at the Bataclan theatre where 80 died in an attack while fans watched a rock concert, told CNN: "I saw two terrorists from my point of view with AK-47s, Kalashnikovs, entering the concert room and firing randomly to the crowd. People yelled, screamed, and everybody lied on the floor. It lasted for ten minutes.
"Ten minutes ... ten horrific minutes where everybody was on the floor covering their head. We heard so many gunshots and the terrorists were very calm, very determined. They reloaded three or four times their weapons. They didn't shout anything. They didn't say anything.
"They were unmasked and wearing black clothes and they were shooting at people on the floor, executing them."
WHAT WE KNOW SO FAR:
- At least 127 dead, and fears death toll could be around 140
- At least five locations targeted in suicide bombings and shootings
- Around 80 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
- Eight extremists killed, all attackers thought to be dead
- Manhunt under way for accomplices
- David Cameron to chair meeting of Government Cobra committee
Earlier on Saturday Islamic State reportedly released an undated video threatening to attack France if bombings of its fighters continue, according to Reuters.
The group called on French Muslims to carry out attacks, and said the bloodbath was designed to show France it will remain a top target if it continues its activity bombing the terror group's fighters, according to Reuters.
A manhunt is under way for accomplices of gunmen who targeted a concert hall and the French national football stadium and sprayed the terraces of bars and restaurants with gunfire in at least six separate attacks. Eight "extremists" have so far been killed.
David Cameron has warned "we must be prepared for a number of British casualties" from the atrocity as he condemned the "brutal and callous murderers".
All schools, museums, libraries, gyms, swimming pools and food markets in Paris will be closed on Saturday.
Soldiers among the 1,500 extra troops deployed in Paris
Speaking after an emergency meeting of senior government and security officials at the Elysee Palace, Mr Hollande announced three days of national mourning and vowed that France would be "pitiless" in its response to terrorism.
French authorities said they believed all eight of those involved in the attacks were dead - seven of them killed by suicide bombs - but Paris's chief prosecutor said it was possible other terrorists were still on the run.
Policing was being strengthened at ports and major events in the UK, and Prime Minister David Cameron was due to chair a meeting of the Government's Cobra emergency committee which could raise the official assessment of the threat from international terrorism from its current "severe" level.
The Queen has sent a message to President Hollande, saying: "Prince Philip and I have been deeply shocked and saddened by the terrible loss of life in Paris. We send our most sincere condolences to you, the families of those who have died and the French people."
The Prince of Wales condemned the Paris terrorist atrocities as "bestial attacks" and said he wanted to express his "utter, total horror" at what had happened.
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