An angry President Francois Hollande on Saturday promised a "merciless" response to a wave of attacks by gunmen and bombers that killed 128 people across Paris, describing the assault claimed by ISIS as an act of war against France.
In the worst attack, a Paris city hall official said four gunmen systematically killed at least 87 people at a rock concert by an American band at the Bataclan concert hall before anti-terrorist commandos launched an assault.
Some 40 more people were killed in five other attacks in the Paris region, the official said, including a double suicide bombing outside the Stade de France stadium, where Hollande and the German foreign minister were watching a soccer game.
The assaults came as France, a founder member of the U.S.-led coalition waging air strikes against ISIS in Syria and Iraq, was on high alert for terrorist attacks, raising questions about how the attacks were able to occur.
It was the worst such attack in Europe since the Madrid train bombings of 2004, in which 191 died.
Hollande said the attacks were organised from abroad by ISIS, with internal help. Investigators were focusing on to what extent the militants were from France or from abroad.
Sources close to the inquiry said one of the dead gunmen was French with ties to Islamist militants.
The holder of a Syrian passport found near the body of one gunman passed though the Greek island of Leros in October, a Greek minister said. A Greek police source said the passport's owner was a man who had arrived in Leros with 69 refugees and had his fingerprints taken. Police declined to give his name.
The Paris attacks are sure to become a factor in the debate raging in Europe about how to handle the migrants crisis fuelled by the conflict that has emerged from the uprising in Syria.
In a sign of potential divisions ahead, Poland said that the attacks meant it could not now take its share of migrants under a European Union plan. Many of the migrants currently flooding into Europe are refugees from Syria.
Turkish President Tayyip Erdogan urged world leaders gathered for a summit in Turkey on Saturday to prioritise the fight against terrorism, saying the Paris attacks showed the time for words was now over.
Hollande pulled out of the meetings but told Erdogan by telephone that his foreign and finance ministers would attend.
"Faced with war, the country must take appropriate action," Hollande said after an emergency meeting of security chiefs. The president also announced three days of national mourning.
"France will be merciless towards these barbarians from Daesh," he said, using an Arab acronym for ISIS.
During a visit to Vienna, U.S. Secretary of State John Kerry said "we are witnessing a kind of medieval and modern fascism at the same time".
In its claim of responsibility, ISIS said the attacks were a response to France's military campaign.
It also distributed an undated video in which a militant said France would not live peacefully as long as it took part in U.S.-led bombing raids against the ISIS.
"As long as you keep bombing you will not live in peace. You will even fear travelling to the market," said a bearded Arabic-speaking militant, flanked by other fighters.
A French government source told Reuters there were 127 dead, 67 in critical condition and 116 wounded. Six attackers blew themselves up and one was shot by police. There may have been an eighth attacker, but this was not confirmed.
The attacks, in which automatic weapons and explosives belts were used, lasted 40 minutes.
"The terrorists, the murderers, raked several cafe terraces with machine-gun fire before entering (the concert hall). There were many victims in terrible, atrocious conditions in several places," police prefect Michel Cadot told reporters.
STATE OF EMERGENCY
Hollande declared a national state of emergency, the first since World War Two. Border controls were temporarily reimposed to stop perpetrators escaping.
Local sports events in Paris were suspended, stores closed, the rock band U2 cancelled a concert, and schools, universities and municipal buildings were ordered to stay shut.
Sylvestre, a young man who was at the Stade de France when bombs went off there, said he was saved by his cellphone, which he was holding to his ear when debris hit it.
"This is the cell phone that took the hit, it's what saved me," he said. "Otherwise my head would have been blown to bits," he said, showing the phone with its screen smashed.
Emergency services were mobilised, police leave was cancelled, 1,500 army reinforcements were drafted into the Paris region and hospitals recalled staff to cope with casualties.
Radio stations warned Parisians to stay at home and urged residents to give shelter to anyone caught out in the street.
France has been on high alert since Islamist gunmen attacked the satirical weekly Charlie Hebdo and a kosher supermarket in January, killing 18 people.
Those attacks briefly united France in defence of freedom of speech, with a mass demonstration of more than a million people. But that unity has since broken down, with far-right populist Marine Le Pen gaining on both mainstream parties by blaming immigration and Islam for France's security problems.
It was not clear what political impact the latest attacks would have less than a month before regional elections in which Le Pen's National Front is set to make further advances. The governing Socialist Party and the National Front suspended their election campaigns.
U.S. President Barack Obama and German Chancellor Angela Merkel led a global chorus of solidarity with France.
France ordered increased security at its sites abroad. Britain, Germany, Italy, Russia, Belgium, Hungary and the Netherlands tightened security measures.
British police said the evacuation of London's Gatwick Airport on Saturday was connected to the discovery of a possible firearm in a bin and a 41-year-old man from France was arrested.
Julien Pearce, a journalist from Europe 1 radio, was inside the Bataclan when the shooting began.
In an eyewitness report posted on the station's website, Pearce said several very young individuals armed with assault rifles entered the hall during a performance by Californian rock group Eagles of Death Metal and started "blindly shooting at the crowd".
"There were bodies everywhere," he said.
The gunmen shot their victims in the back, finishing some off at point-blank range before reloading and firing again, Pearce said, after escaping into the street by a stage door, carrying a wounded girl on his shoulder.
Toon, a 22-year-old messenger who lives near the Bataclan, was going into the concert hall with two friends at around 10.30 p.m. (2130 GMT) when he saw three young men dressed in black and armed with machine guns.
One of the gunmen began firing into the crowd. "People were falling like dominoes," he told Reuters. He saw people shot in the leg, shoulder and back, with several lying on the floor, apparently dead.