A series of attacks targeting young concert-goers, soccer fans and Parisians enjoying a Friday night out at popular nightspots killed at least 120 people in the deadliest violence to strike France since the Second World War. President François Hollande condemned it as terrorism and pledged that France would stand firm against its foes.

More than 200 were injured in at least six separate attacks around the capital Friday. The worst carnage was at a concert hall hosting an American rock band where scores of people were held hostage and attackers ended the standoff by detonating explosive belts. Police who stormed the building encountered a bloody scene of horror inside.

A person is evacuated from the Bataclan concert hall after more than 100 people were killed in a series of attacks across Paris — the deadliest violence to strike France since the Second World War. (Thibault Camus/Associated Press)

French police said they believe all of the attackers involved in the shootings and bombings are dead. The Associated Press reported that eight militants had been killed, seven of them in suicide bombings.

The Paris prosecutor's office spokeswoman Agnes Thibault-Lecuivre told The Associated Press that the eighth attacker was killed by security forces at the concert hall. She could not exclude the possibility that some attackers might still be at large. Authorities are searching for possible accomplices.

People hug on the street near the Bataclan concert hall. (Christian Hartmann/Reuters)

The attack unfolded with two suicide bombings and an explosion outside the national stadium during a soccer match between the French and German national teams. Within minutes, according to Paris police chief Michel Cadot, another group of attackers sprayed cafés outside the concert hall with machine gunfire, then stormed inside and opened fire on the panicked audience. As police closed in, they detonated explosive belts, killing themselves.

One witness told Radio France that the attackers came into the venue, where 1,500 people were attending a rock concert, and started shooting.

"They shot right into the crowd while shouting 'Allah Akbar' — with shotguns, I think … It was hell," one witness at Bataclan told Radio France, according to AFP.

A woman is evacuated from the Bataclan concert hall. (Thibault Camus/AP)

In addition to the deaths at the concert hall, dozens of people were killed at the other attack sites.

"This is a terrible ordeal that, again, assails us," Hollande said. "We know where it comes from, who these criminals are, who these terrorists are."

Victims are seen from the shooting at the Belle Equipe restaurant, where 18 people died. It was one of three restaurants attacked on Friday. (Anne Sophie Chaisemartin/Associated Press)

Paris prosecutor François Molins said the investigation into the attacks will try to determine what happened at six sites around the city, including the Bataclan, where anywhere from 87 to 112 people were killed, according to various reports.

The other attack sites were:

The Stade de France in Saint-Denis north of Paris, where, French media reported, four people were killed in two suicide attacks and an explosion, including three attackers.

La Belle Equipe bar, 92 rue de Charonne Blvd. in the 11th arrondissement, where 18 people died.

Le Carillon restaurant, 18 Alibert St., and Le Petit Cambodge, 20 Alibert St., in the 10th arrondissement, where 14 died in total.

Voltaire Blvd., where one person was killed.

De la Fontaine au Roi St., where five deaths were reported.

'It's a horror'

According to reports, Hollande was at the soccer game and was evacuated from the stadium soon after reports of the attacks emerged.

"We will lead the fight. It will be ruthless," Hollande said outside the concert hall shortly after security forces had stormed the building, ending the siege.

A map shows some of the attack sites in Paris: the national stadium in the northern suburb of St. Denis; two restaurants on Alibert Street; the Belle Equipe restaurant on Charonne Boulevard; and the Bataclan concert hall on Voltaire Boulevard. (Canadian Press)

"It was carnage," Marc Coupris told the Guardian newspaper after he was freed from the hostage-taking. "It looked like a battlefield, there was blood everywhere, there were bodies everywhere."

Terrifying: Paris gunmen firing at French civilians. Just now. <a href="https://twitter.com/hashtag/ParisAttacks?src=hash">#ParisAttacks</a> <a href="https://t.co/sTWhi3Pwvc">pic.twitter.com/sTWhi3Pwvc</a> —@cjwerleman

Gunfire and explosions had been heard outside the concert venue shortly before the police assault ended.

"It was horrible, there were so many corpses, I just can't talk about it," another man told the Guardian as he left the Bataclan venue.

French President François Hollande, centre, flanked by French Interior Minister Bernard Cazeneuve, rear left, French Prime Minister Manuel Valls, right, and Speaker of the French National Assembly Claude Bartolone visit Bataclan shortly after security forces stormed the venue. (Miguel Medina/AFP/Getty)

A woman who was at a bar near Bataclan said people ran into the bar, fleeing the initial shooting. "They were panicked, wounded, screaming, blood was running all over them. People were having panic attacks; it was horrific."

The attacks also prompted Hollande to declare a state of emergency, and he announced that he was closing the country's borders, although officials later said they were just re-imposing border checks that had been removed after Europe created its free-travel zone in the 1980s. France's foreign ministry said airports in that country would remain open and said train travel will continue.

Hollande also cancelled his trip to the G20 summit in Turkey, which begins Sunday.

French fire brigade members aid an injured individual near the Bataclan concert hall. (Christian Hartmann/Reuters)

Hollande announced he had deployed military around Paris.

"It's a horror," Hollande earlier said in a televised statement.

He said the country needs to stand in solidarity and remain calm despite the attacks.

Wounded people are evacuated outside the Bataclan concert hall. (Yoan Valat/EPA)

In Canada, Prime Minister Justin Trudeau said that so far, there was no information that any Canadians were victims of the attacks.

French president vows to launch a 'ruthless' retaliation after more than 100 people were killed in multiple deadly attacks around Paris 2:09

"These terrorist attacks are deeply worrying and, obviously, unsettling to people around the world," Trudeau said before leaving for the G20 summit in Antalya, Turkey.

"We have offered all of our help and support to the government of France."

Several police agencies investigating

An Associated Press reporter who was 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.

Rescue personnel work near covered bodies outside a Paris restaurant that was one of the sites of multiple explosions and shootings Friday. (Philippe Wojazer/Reuters)

AFP reported that French authorities are investigating the attacks in connection with a terrorist plot. Three different security forces will be involved in the investigation, including the anti-terror unit of the Paris division of the French national police.

Rescue workers outside Le Carillon, one of two restaurants on Alibert St. where shootings occurred, leaving 14 dead. (Philippe Wojazer/Reuters)

The attack comes as France has heightened security measures ahead of a major global climate conference that starts in two weeks, out of fear of violent protests and potential terrorist attacks.

Police officers detain a man at the scene of the hostage situation at the Bataclan before officers stormed the venue. ((Yoan Valat/EPA))

Emilioi Macchio, from Ravenna, Italy, was at the Carillon bar near the restaurant that was targeted, having a beer on the sidewalk when the shooting started. He said he didn't see any gunmen or victims, but hid behind a corner then ran away.

"It sounded like fireworks," he said.

People leave the Stade de France stadium where a match between France and Germany was taking place when multiple attacks broke out nearby.

U.S. President Barack Obama described the incident as "outrageous attacks" on "our oldest ally."

Justin Trudeau reacts to multiple deadly shootings, explosions around French capital 4:49

"Obviously, those of us here in the United States know what it's like. We have gone through these kinds of episodes ourselves.

"And whenever these kinds of attacks happened, we've always been able to count on the French people to stand with us. They have been an extraordinary counter-terrorism partner. And we intend to be there with them in that same fashion."