Five people believed to have trained as Islamist militants in Pakistan's troubled Afghan border region have been arrested in and around Paris.
Some of those arrested were picked up in the suburb of Roissy, where France's largest airport is located, security sources said on condition of anonymity.
Police and intelligence officers have been questioning the suspects.
Parts of western Pakistan along the Afghan border have long been used as bases by international militant groups.
Some of the suspects are apparently linked to death threats made a few weeks ago against the rector of the Grand Mosque of Paris, Dalil Boubakeur, France's RTL radio reports.
Al-Qaeda leader Osama Bin Laden warned France last month that its planned ban on the Islamic full-face veil in public places and its involvement in the war in Afghanistan justified attacks on its nationals.
French Interior Minister Brice Hortefeux later said that the country faced a real terror threat and he urged "total vigilance".