PARIS - Police were holding for questioning the father and brother of a man who took part in Friday's attacks in Paris, French media reported on Sunday, as the hunt continued for others involved in the shootings in which 129 people died.

A judicial source confirmed police were holding people close to one of the attackers, seven of whom died in the assault, which has been claimed by Islamic State.

Police have identified one of the men as a Frenchman, on whom authorities had a dossier that marked him as a potential Islamist militant.

The reports said searches were also being conducted in the relatives' homes in the northeastern Aube region and in Essonne, south of Paris.

French prosecutors said on Saturday that three coordinated teams appeared to have carried out the wave of attacks across Paris. They were the worst in Europe since the Madrid train bombings of 2004, in which Islamists killed 191 people.

Friday's attacks were described as an "act of war" by President Francois Hollande.

The bloodshed came as France, a founder member of the US-led coalition waging air strikes against Islamic State in Iraq and Syria, was already on high alert for terrorist attacks.