PARIS — Three teams of Islamic State attackers acting in unison carried out the terrorist assault in Paris on Friday night, officials said Saturday, including one assailant who may have traveled to Europe on a Syrian passport along with the flow of migrants.
“It is an act of war that was committed by a terrorist army, a jihadist army, Daesh, against France,” President François Hollande told the nation from the Élysée Palace, using an Arabic acronym for the Islamic State. “It is an act of war that was prepared, organized and planned from abroad, with complicity from the inside, which the investigation will help establish.”
As the death toll rose to 129 — with 352 others wounded, 99 of them critically — a basic timeline of the attacks came into view.
The Paris prosecutor, François Molins, said the attackers were all armed with heavy weaponry and suicide vests. Their assault began at 9:20 p.m. Friday, when one terrorist detonated a suicide bomb outside the gates of the soccer stadium on the northern outskirts of Paris. It ended at 12:20 a.m. Saturday when the authorities stormed a concert hall, the Bataclan. One attacker there was killed; two others detonated suicide vests. Inside the hall, 89 people, who had been listening to a rock band, had been shot to death.
The man with the Syrian passport — which Greek officials said had been registered at the Aegean island of Leros on Oct. 3 — was 25, and died at the stadium. Another assailant, who died at the concert hall, was 29 and a native of Courcouronnes, about 20 miles south of Paris. He had a criminal record and was known to be involved in extremist Islamic ideology, Mr. Molins said.
The hunt for possible accomplices of the terrorists gained steam on Saturday. Officials in Belgium announced three arrests, one of them linked to a rental car found in Paris. In Germany, the police were exploring whether a man they arrested last week with weapons in his car and his GPS navigator set for Paris was linked to the attacks. But it remained unclear how a plot of such sophistication and lethality could have escaped the notice of intelligence agencies, both in France and abroad.
Mr. Hollande declared three days of national mourning, and said that military troops would patrol the capital. France remained under a nationwide state of emergency.
Mr. Hollande vowed to “be unforgiving with the barbarians from Daesh,” adding that France would act within the law but with “all the necessary means, and on all terrains, inside and outside, in coordination with our allies, who are, themselves, targeted by this terrorist threat.”
The attacks, and the possibility that the Islamic State was to blame, promised to further traumatize France and other European countries already fearful of violent jihadists radicalized by the conflicts in Syria and elsewhere.