A series of attacks across Paris on Friday thrust the city into chaos, killing at least 129 and injuring 352 in the deadliest violence to reach France since World War II.

French President Francois Hollande vowed to respond to what he called a terrorist attack, according to news agency Agence France-Presse: "We are going to lead a war; it will be pitiless."

Hours after explosions and shootings erupted at multiple sites, police raided a concert hall where gunmen were holding hostages, police and medical officials said. Earlier, a French police official said at least 100 people were killed inside the venue, which was scheduled to host a band from California on Friday night.

On Saturday, the Paris prosecutor said 89 of the 129 people killed in the attacks, were slain inside the Bataclan concert hall. All eight attackers were believed to be dead, seven in suicide bombings.

"It's a horror," Hollande earlier told his nation in a televised address, declaring a state of emergency and shuttering the nation's border, NBC News reported. U.S. President Barack Obama called the attacks on Paris an "outrageous attempt to terrorize innocent civilians."

[NATL] PHOTOS: Terror Attacks Leave Paris Shellshocked

There was no immediate claim of responsibility for the series of attacks, which recalled the horrors of a recent, devastating attack at satire magazine Charlie Hebdo. Police were urging Parisians to stay in their homes and closed all metro stations in the city.