"The state will mobilise all its means to combat these violent acts," Hollande said after a night of unrest that left 16 police officers injured, a primary school badly damaged by fire and a sports centre completely destroyed.

"Security is not only a priority for us, it is an obligation."

Hollande's Interior Minister Manuel Valls was due to visit Amiens later on Tuesday.

The riot, which the local mayor has linked to rising social tension against a backdrop of a deteriorating economy, cast a shadow over Hollande's
celebration of 100 days since he was elected.

Hollande was in the southeastern village of Pierrefeu-du-Var to pay tribute to two female police officers who were shot dead in the line of duty in June.

The visit was intended to underline the Socialist president's support for the police and his determination to address public concerns over crime.

But it risked backfiring after the father of one of the two murdered policewomen denounced it as a public relations stunt.

Claude Berthaut, whose daughter Audrey was shot dead alongside her colleague Alicia Champlon, said: "I regret that he didn't come before but has
instead come for communications purposes 100 days after his election.

"In my mind, it is two months too late."    

Hollande sent an official from his private office to represent him at the funerals of the two officers, citing prior commitments.