Seven French tourists have been kidnapped by gunmen in Cameroon near the border with Nigeria.
President Francois Hollande said they belong to the same family and were probably taken to northern Nigeria.
He indicated the Boko Haram group may have been responsible.
"I see the hand of Boko Haram in that part of Cameroon and that is worrying enough for us to mobilise," Mr Hollande said.
He said everything possible was being done to rescue the family.
The BBC reports the family was returning from a visit to Waza National Park on Tuesday when they were captured by men on motorcycles, about 10km from the Nigerian border.
On Sunday another group, Ansaru, claimed the abduction of seven foreign workers in Nigeria.