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 apartment at Rue Miollis, north of the central station, where one individual was arrested.
The driver weilded a gun as his 25-tonne white truck zigzagged along the seafront Promenade des Anglais as a fireworks display marking the French national day ended just after 10:30 p.m., in what President Francois Hollande called a terrorist act.
The attacker, identified by a police source as a 31-year-old Tunisian-born Frenchman, also opened fire before officers shot him dead. The man was not on the watch list of French intelligence services, but was known to the police in connection with common crimes such as theft and violence, the source said.
According to the BBC, 202 people were injured in the massacre, 52 of whom remain in a critical condition, and 25 on life support.
