A fire has swept through a bar in northern France, killing at least 13 people and injuring six others.

Police say the fire broke out at a birthday party at the Cuba Libre in the city of Rouen in Normandy.

The blaze was sparked by the candles of a birthday cake, which ignited the polystyrene ceiling of the basement room where the celebrations were taking place.

The victims were poisoned by a toxic mix of gases released by the burning plastic, a senior police official told AFP.

"There wasn't an explosion, it was candles used for a birthday party," he said.

The blaze started at around midnight at the Cuba Libre bar in the city centre, and the firemen were at the scene by 00:20am local time.

French interior minister Bernard Cazeneuve gave an initial count of 13 dead and six injured.

"A fire broke out in a bar in the city centre of Rouen this evening. According to an initial investigation, 13 are dead and six are injured, and more than 50 firemen attended the scene," Mr Cazeneuve said in a statement.

"An inquiry is underway to establish the cause of the fire," he added.

One of the injured was in a critical condition, Yvan Cordier, the secretary general of the Seine-Maritime prefecture, told AFP.

Local official Laurent Labadie, who was at the scene of the fire, described the blaze as accidental.

Jittery France is on edge after a series of recent attacks by jihadists affiliated with Islamic State of Iraq and the Levant, including the killing of a priest in nearby Saint-Etienne-du-Rouvray.

The priest's funeral was held in Rouen's cathedral and was attended by more than 2,000 mourners shocked by the brutal killing of the elderly clergyman.