At least 100 people died in a popular Paris concert hall where attackers seized hostages Friday, an official said, one of at least six terror attacks that gripped the city, The Associated Press is reporting.

Earlier, police launched an assault on the Paris concert venue where hostages are being executed one-by-one, Fox News reported.

Several dozen people were killed Friday in the deadliest attacks to hitParis since World War II, French President Francois Hollande said, announcing that he was closing the country’s borders and declaring a state of emergency.

At least 35 people died in shootings and explosions at multiple sites, many of them in a popular concert hall where patrons were taken hostage, police and medical officials said. The series of attacks gripped the city in fear and recalled the horrors of the Charlie Hebdo carnage just 10 months ago.

A police official said 11 people were killed in a Paris restaurant in the 10th arrondissement, and other police officials said at least twice that number died elsewhere, primarily in the Bataclan music venue, where the hostages were taken. It was unclear how many people were in the hall; one official said there were around 100, while another said there were far fewer.

The officials spoke on condition of anonymity because they were not authorized to be publicly named in the quickly moving investigation.

There was no immediate claim of responsibility for the series of attacks.

Hollande, in a televised address, said the nation would stand firm and united against the attackers.

He also said security forces are assaulting one of the sites hit by Friday’s attacks, without elaborating.

“It’s a horror,” he said.

U.S. President Barack Obama, speaking to reporters in Washington, called the attacks on Paris “outrageous attempt to terrorize innocent civilians” and vowed to do whatever it takes to help bring the perpetrators to justice.

Also late Friday, two explosions were heard outside the Stade de France stadium north of Paris during a France-Germany friendly football match.

A police official confirmed one explosion in a bar near the stadium. It was not known if there were casualties.

An Associated Press reporter in the stadium Friday night heard two explosions loud enough to penetrate the sounds of cheering fans. Sirens were immediately heard, and a helicopter was circling overhead. Hollande, who was in the stadium, was evacuated to an emergency meeting.