PARIS (AFP) - The attack on a French police officer outside Paris's famed Notre Dame cathedral by a hammer-wielding man was an "isolated act," government spokesman Christophe Castaner said on Wednesday (June 7).

Tuesday's attacker had "never showed any sign of radicalisation," he told RTL radio, but stressed that the investigation was at an early stage.

The man had shouted "this is for Syria" when he attacked the police officer.

Police sources said the officer sustained minor neck injuries in the assault.

The assault comes with France on high alert after terrorists killed seven people in London on Saturday.