French police arrested three people in Nice early on Saturday in connection with the probe into the Bastille day attack that killed at least 84 people when a truck rammed into crowds in the Riviera city, police sources said.

French authorities were still trying to determine whether the 31-year old Tunisian driver of the vehicle had acted alone or with accomplices, and whether his motives were connected to radical Islam.

The arrests concerned the attacker's "close entourage", the sources said, and were made in two different areas of Nice. A Reuters reporter saw about 40 elite police raid a small appartment at Rue Miollis, north of the central station, where one individual was arrested.-Reuters