France: Eiffel Tower goes dark

The Eiffel Tower stood dark in a symbol of mourning Saturday night as France struggled to absorb the deadliest violence on its soil since World War II: coordinated gun-and-suicide bombing attacks across Paris that left at least 129 people dead and 352 injured.

President Francois Hollande vowed that France would wage "merciless" war on the Islamic State of Iraq and Syria (ISIS), which claimed responsibility for the mayhem, as investigators raced to track down their accomplices and uncovered possible links to networks in Belgium and Syria.

Paris prosecutor Francois Molins said three groups of attackers, including seven suicide bombers, carried out the "act of barbarism" that shattered a Parisian Friday night.

He said the attackers in the Bataclan concert hall, where 89 people died, mentioned Syria and Iraq during their rampage. Of the hundreds wounded in the six attacks, 99 were in critical condition.

Seven attackers launched gun attacks at Paris cafes, detonated suicide bombs near France's national stadium and killed hostages inside the concert venue during a show by an American rock band -- an attack on the heart of the pulsing City of Light.

Ahsan Naeem, a 39-year-old filmmaker, said he's been to many of the places that were attacked Friday.

"I've seen dozens of gigs at the Bataclan. Eaten at the Petit Cambodge. Sat outside Le Carillon on so many nights," said Naeem, who has lived in Paris for seven years. "All those places will have been full of my people. My friends. My acquaintances." 

Late Saturday, a crowd of up to 250 people gathered for an impromptu candlelight vigil at the Place de la Republique, the site of a massive demonstration in the wake of the Charlie Hebdo killings earlier this year. Adrien Chambel, a 27-year-old law student, said the crowd was much sparser than in January. "You feel that people are petrified," Chambel said.

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 ISIS. He said France - which is part of a U.S.-led coalition bombing suspected ISIS targets in Syria and Iraq and also has troops fighting Islamic militants in Africa -- "will be merciless toward the barbarians of Islamic State group."

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

The statement called Paris "the capital of prostitution and obscenity" and mocked France's air attacks in Syria and Iraq, saying France's air power was "of no use to them in the streets and rotten alleys of Paris."

A U.S. intelligence source told Milton investigators have so far seen no insider knowledge in the chatter or communications that is being intercepted to verify who was involved. While there have been people saying glowing things about the Paris attack, no one has revealed information about the attack that only the attackers would have knowledge of, the source said.

In New York, the Empire State Building went dark for a second night in sympathy for people of Paris, while One World Trade Center was lit with the colors of the French flag.