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".
The Nice attack which killed 86 people further traumatized a country already reeling from a series of jihadist attacks including the November 2015 massacre in Paris.