Security has been beefed up at Christmas markets throughout France following the carnage in Berlin on Monday, French Interior Minister Bruno Le Roux said.
"Security at Christmas markets was immediately reinforced" after a lorry ploughed into a Berlin Christmas market killing at least nine people, he said.
The scenes in Berlin were reminiscent of an attack in the French Riviera city of Nice in July in which Tunisian extremist Mohamed Lahouaiej Bouhlel ploughed a 19-tonne truck into a seafront crowd at a fireworks display.
President Francois Hollande said the French people "share in the mourning of the Germans in the face of this tragedy that has hit all of Europe".
Most large French cities host thriving Christmas markets at this time of year, but even before the bloodshed in Berlin security at the events had been tight. Armed police and soldiers have been patrolling the Christmas market on the Champs-Elysées in Paris, while several festive markets have been reduced in size with cordons set up outside. Several markets are pedestrian only with cars from banned from the area.
Last month French counter-terror police said they had thwarted a terror attack in the Paris area after they made a series of arrests in Strasbourg and Marseille.
Public prosecutor Francois Molins said police had found automatic weapons and evidence of allegiances to the ISIS group, after raids in Strasbourg and Marseille, and the group was planning to strike in the Paris area on December 1st.
Police sources told AFP that members of the cell had researched bars in north east Paris as well as the Champs Elysées Christmas market. They were also believed to be targeting Disneyland.
The Nice attack which killed 86 people further traumatised a country already reeling from a series of jihadist attacks including the November 2015 massacre in Paris.