The Islamic State terror group has claimed responsibility for a string of bomb and gun attacks in Paris which killed at least 127 people and wounded 180 more.
French president Francois Hollande has denounced the attacks as an “act of war” and vowed that France would be “pitiless” in its response to the “absolute barbarity”.
Speaking after an emergency meeting of senior government and security officials at the Elysee Palace, Mr Hollande declared three days of national mourning.
Policing was being strengthened at ports and major events in the UK, and Prime Minister David Cameron was chairing a meeting in Downing Street of the Government’s Cobra emergency committee which could raise the official assessment of the threat from international terrorism from its current “severe” level.
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 almost simultaneous attacks.
In a televised address to the nation, Mr Hollande said the attacks were “committed by a terrorist army, the Islamic State group, a jihadist army, against France, against the values that we defend everywhere in the world, against what we are: a free country that means something to the whole planet”.
He said the attacks were “prepared, organised and planned from abroad, with complicity from within the country”.
The French army and security forces were mobilised “at the highest possible level” and France would “act by all means anywhere, inside or outside the country” against the terrorists responsible, he said.
In a night of carnage in the French capital:
:: Police stormed the Bataclan concert hall where hostages were being held, but attackers wearing suicide belts blew themselves up, leaving 80 people feared dead. A witness said one of the gunmen shouted “Allahu Akbar” and said “This is for Syria”
:: Two suicide attacks and a bombing took place at the Stade de France stadium, where Mr Hollande was among thousands of football fans watching the national side play a friendly against Germany
:: Gunmen targeted bars and restaurants in the 10th and 11th arrondissements of central Paris
:: As many as 18 people died when the terrace of La Belle Equipe was sprayed with gunfire, while around 14 people were killed at Le Carillon bar-cafe. There were also shootings at the nearby Cambodian restaurant Le Petit Cambodge and the La Casa Nostra pizzeria
A message issued in Arabic and French by IS – also known as Isil, Isis and Daesh – said that “eight brothers wearing explosive belts and carrying assault rifles” had targeted “the capital of abominations and perversions and those who carry the crusader banner in Europe”.
The locations of the killings were “meticulously selected in advance in the heart of the French capital”, said the statement, which described the music fans at the Bataclan as “idolators at a festival of perversity”.
In an apparent reference to France’s participation in air strikes against IS strongholds in Syria, the statement continued: “France and those who follow the same path must know that they will remain the principal targets of Islamic State and will continue to smell the scent of death for having… struck Muslims in the territory of the caliphate with their aircraft.”
A state of emergency was declared in France after the worst night of violencein the country since the Second World War.
Police leave was cancelled and 1,500 extra soldiers have been mobilised to guard official buildings and religious sites, while controls have been re-imposed at the country’s borders and public facilities including schools have been closed. All public demonstrations were banned in the Paris region until Thursday.
Mr Hollande, who has cancelled a planned visit to Turkey for the G20 summit this weekend, is to address both houses of the French parliament at Versailles on Monday.
Messages of sympathy and support were issued by world leaders, while ordinary people around the globe turned to social media to express their shock.
Mr Cameron described the attacks as “horrifying and sickening” and vowed the UK will do “whatever we can to help”.
The Prince of Wales condemned the Paris terrorist atrocities as “bestial attacks” and said he wanted to express his “utter, total horror” at what has happened.
US president Barack Obama said the violence in the French capital was “an attack on all of humanity”, while the Vatican condemned it “in the most radical way”.
The foreign ministry of Iran – whose president Hassan Rouhani cancelled a trip to France – said the Paris killers “are not loyal to any type of divine religions – including Islam”.
The Foreign Office said it was in “close touch” with French authorities and was “urgently investigating” whether there were any UK victims.
British police were liaising with their counterparts in Paris on possible lessons for security in the UK.
Metropolitan Police Assistant Commissioner Mark Rowley, the national police lead for counter-terrorism, said there would be a strengthened police presence at ports and major events and on the streets in Britain, and called for “vigilance” from the general public.
US officials said all members of the American rock band Eagles of Death Metal, who were playing a concert at the Bataclan, escaped unhurt.
Scenes of “carnage” were described by witnesses in the concert hall, who said there was “blood everywhere”.
The brother of the band’s drummer, Julian Dorio, told US newspaper the Atlanta Journal Constitution that the musicians hit the floor after seeing gunmen, then fled by a backstage door.
After speaking to his brother by phone, Michael Dorio said: “They saw a man with a machine gun just opening fire.”
Television cameraman Charles Pitt said he was outside a cafe in the city’s 11th arrondissement where people were shot at around 9.10pm local time.
He told BBC News: “I had literally gone about 30 metres when, I thought it was a firecracker to start with, and then it went on and it got louder.
“It went on for a minute. Everybody dived for cover, thinking it was gunfire. Then there was a pause for about 15 seconds and then it all started up again.
“Then it calmed down a bit and I walked back to the front of the cafe and there was a whole pile of bodies, probably about seven on the left-hand side and four that had been sitting on the tables outside on the right-hand side, and a lot of injured.
“I saw a woman who had obviously been shot in the leg.”
The Foreign Office advised Britons to “exercise caution in public places” following the attacks, and people with concerns about British friends or relatives in Paris can call 020 7008 1500 for assistance.
French authorities have advised people in Paris to remain in their homes.
Disneyland Paris was closed for the day and all sporting events in the French capital have been postponed, including a rugby union Champions Cup tie involving Scotland’s Glasgow Warriors.
Channel Tunnel train operator Eurostar said services would run to Paris, but passengers due to travel on Saturday were being offered a free ticket exchange.
The attacks come after the Charlie Hebdo atrocity in January, which saw 12 people killed after gunmen stormed the Paris offices of the satirical magazine.
They also came a day after Islamic State militant Mohammed Emwazi, known as Jihadi John, was targeted in a US air strike in Syria. It is not clear if there is any link.