The truck driver who killed 84 people in the French city of Nice showed a "clear, recent interest" in radical Islam, the Paris prosecutor said Monday, confirming the attack was "premeditated".

The investigation showed Mohamed Lahouaiej Bouhlel had trawled the internet for information on a terror attack in the US city of Orlando and on the killing of a police couple in a Paris suburb last month, Francois Molins said.

A search of his computer also found violent images "linked to radical Islam", he told a press conference in Paris.

However he said no clear link had been established between the father of three and ISIS, which claimed the Bastille Day carnage.

(AFP)