A French family of seven - three adults and four children - have been kidnapped in northern Cameroon, President Francois Hollande confirmed
Mr Hollande indirectly suggested that the Boko Haram group may have had a role in the kidnapping.
French minister Laurent Fabius said it "probably was this sect Boko Haram".
Details of the kidnapping were not immediately clear.
Mr Hollande, speaking during a visit to Greece, warned French citizens in the region "to avoid exposing themselves".
A French official close to the embassy in Cameroon said the group was believed to have been taken from northern Cameroon to Nigeria, where a little-known extremist group claimed responsibility for a separate abduction of seven foreigners on Monday.
Boko Haram has launched a guerrilla campaign of bombings and shootings across Nigeria's predominantly Muslim north.
It is blamed for at least 792 killings last year alone.
"If everything is confirmed, this signifies that the fight against terrorist groups is a necessity," Mr Fabius said in Paris.
"There is a battle to be led by the international community against terrorist groups and narco-terrorists," a reference to the trafficking in drugs, cigarettes and other commodities that has flourished in northern Mali under the extremists.