PARIS: France on Wednesday urged its citizens to leave northern Cameroon after seven members of a French family were seized in a kidnapping officials suspect was carried out by Nigerian Islamist group Boko Haram.

The family -- a couple, their children aged five, eight, 10 and 12 and an uncle -- were snatched in northern Cameroon by six gunmen on three motorbikes on Tuesday and officials said they had been taken across the border into Nigeria.

The French foreign ministry in a notice urged citizens in the far north "to leave the area as quickly as possible" and advised against travel to areas bordering Nigeria until further notice.

The ministry could not say how many French citizens are believed to be in the north but 6,200 in total are registered as living in Cameroon.

French Defence Minister Jean-Yves Le Drian pointed the finger at Boko Haram but said it was not clear whether the kidnapping was linked to France's intervention against Islamist rebels in Mali.

"We believe that the Boko Haram sect carried out this kidnapping, but we don't yet have a claim of responsibility," Le Drian told France 2 television.

"These are groups that claim the same fundamentalism, who use the same methods, whether it's in Mali, Somalia or Nigeria," he said.