Paris attacks: Suicide bomber identified; ISIS claims responsibility for 129 dead

Paris (CNN)Authorities in France and Belgium took people into custody Saturday in the aftermath of the worst violence in France since World War II, a series of terror attacks that killed more than 120 people.

ISIS claimed responsibility for the horrific Paris attacks, for which France vowed revenge.

President Francois Hollande deemed the shootings and bombings "an act of war." He said early Saturday, "We will lead the fight, and we will be ruthless."

French President vows 'ruthless' response

Belgian authorities made a number of arrests there in the first publicized apprehensions after Friday night's bloodshed, a Belgian Justice Ministry spokeswoman said Saturday.
In Belgium, raids were conducted in the Brussels suburb of Molenbeek-Saint-Jean, Justice Ministry spokeswoman Sieghild Lacoere said. A car rented in Brussels was found near one of the sites of the Paris attacks, and "that's what triggered the raids," Lacoere said.

In all, the raids took place in three homes in Molenbeek-Saint-Jean, a Western intelligence source told CNN.

Police conduct raids in Belgium 02:21

At least one of the raids is connected to the Paris attacks, according to the source, who is in contact with French and Belgian intelligence services. The other raids are connected to individuals known to Belgium intelligence, the source said. Some of the Paris attackers are also known to Belgium intelligence, the source added.

Also Saturday, CNN affiliate BFMTV reported that the father and a brother of one of the attackers had been taken into custody. And AFP reported that the two men were detained after police raided their homes 130 kilometers (81 miles) east of Paris. CNN has not independently verified that the men were picked up by authorities.

One of the suicide bombers in Friday's attacks has been identified as Ismael Omar Mostefai, according to a French member of Parliament. Mostefai lived in Chartres at least until 2012, said Jean-Pierre Gorges, who is mayor of the French town as well as a member of Parliament, via Facebook.