PARIS — Three teams of extremists carried out the coordinated gun-and-suicide bombing attacks across Paris that left 129 people dead and 352 injured, a French prosecutor said Saturday.

Paris prosecutor Francois Molins said 99 of the injured were in critical condition after the “act of barbarism.” He said the attackers in the Bataclan concert hall, where 89 people died, mentioned Syria and Iraq during their deadly rampage.

French President Francois Hollande has vowed that France will wage “merciless” war on the Islamic State group, after the jihadists claimed responsibility for the attacks Friday night.

Grief, alarm and resolve spread across Europe on Saturday as officials raced to piece together information on the seven attackers. Officials said one was a young Frenchman known to the authorities. In addition, a Syrian passport found near the body of another attacker was linked to a man who entered the European Union through a Greek island last month.

Attackers launched gun attacks at Paris cafes, detonated suicide bombs near France’s national stadium and killed hostages inside a concert hall during a rock show — an attack on the heart of the pulsing City of Light.

“These places are the places we visit every week,” said Ahsan Naeem, a 39-year-old filmmaker who has lived in Paris for seven years. “Streets we walk every day … All those places will have been full of my people. My friends. My acquaintances.”

Hollande, who declared three days of national mourning and raised the nation’s security to its highest level, called the carnage “an act of war that was prepared, organized, planned from abroad with internal help.”

The president said France would increase its military efforts to crush IS. He said France — which is part of a U.S.-led coalition bombing suspected IS targets in Syria and Iraq and also has troops fighting militants in Africa — “will be merciless toward the barbarians of Islamic State group.”

The Islamic State group claimed responsibility in an online statement in Arabic and French circulated by supporters. It was not immediately possible to confirm the authenticity of the admission, which bore the group’s logo and resembled previous verified statements from the group.

The statement mocked France’s involvement in air attacks on suspected IS bases in Syria and Iraq, noting that France’s air power was “of no use to them in the streets and rotten alleys of Paris.”

Many of Paris’s top tourist attractions closed down Saturday, including the Eiffel Tower, the Louvre Museum and the Disneyland theme park east of the capital. Some 3,000 troops were deployed to help restore order and reassure a frightened populace.

Interior Minister Bernard Cazeneuve announced that all public demonstrations would be banned until Thursday and local governments would have the option to impose nightly curfews.

The attacks, on an unusually balmy November Friday evening, struck at the heart of Parisian life: diners in cafes, concertgoers watching a rock band, spectators at a soccer match.

Paris Mayor Anne Hidalgo said the places attacked are ones Parisians love — and ones where they celebrate diversity.