Paris - A young man described as a "psychopath" by the French police has been transferred to the psychiatric hospital after being arrested on Wednesday at the Museum of the Riviera where he was fortified for hours.

The 18-year-old entered the Archaeological Museum in San Rafael at night, and remained there alone and unarmed for four hours before being stopped by police at around 11:00 am. On Wednesday afternoon, his detention was extended and taken to a psychiatric hospital.

The district attorney general, Patrice Campero, told AFP: "The young man is mentally ill, mentally, and was delirious, it is impossible to question him or determine his motives."

A police source said threatening language in Arabic was found on the walls of the building.

He continued: "Nothing suggests threats," but pointed out that "the young man wrote Arabic very badly."

The young man was arrested "without resistance or violence" in the gardens of the museum by special forces elements in Marseille and Nice.