French police have taken into custody four members of the family of a radicalised Islamist who was killed when he rammed a car loaded with guns and a gas bottle into a police van on the Champs-Elysees, a judicial source said Tuesday.

The ex-wife, brother and sister-in-law of Adam Dzaziri were detained on Monday afternoon after police questioned them at the family home near Paris. The assailant's father was also "taken into custody during the evening", the source said.