A black Seat car used by gunmen who fired at people in restaurants during the attacks in Paris on Friday has been found in the eastern suburb of Montreuil, police said Sunday.

Six people close to Omar Ismail Mostefai, who took part in the killings at the Bataclan concert hall and the first of Friday's attackers to be identified, have been detained.

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Among the six were Mostefai's father, brother and sister-in-law, judicial and police sources said.

They are being questioned as part of routine efforts to verify information about the attacker, the sources said.

"It's a crazy thing, it's madness," the brother told AFP on Saturday before being detained, referring to the carnage that left 129 people dead.

The Seat car was used at two of the six locations attacked on Friday -- a bar on rue de la Fontaine-au-Roi where five were killed, and a restaurant on rue de Charonne, where 19 died.