The French foreign ministry has called on its citizens to quit north Cameroon after a family of six and a friend were abducted by gunmen on motorbikes as the holidaymakers drove back from Waza National Park.
French citizens were officially advised not to go to the far north of Cameroon (the shores of Lake Chad) and the border with Nigeria, until further notice.
The captives, including four boys aged four, seven, nine and 11, were kidnapped by a known Nigerian-based "terrorist group" near the border with Nigeria. The president of Cameroon, Paul Biya, pledged all measures would be taken to rescue them.
French president Francois Hollande said the kidnappers may have been with extreme jihadists Boko Haram. Waza National Park is just 150 miles from the Nigerian city of Maiduguri, considered the cradle and the stronghold of the Islamist terrorists.
In January, Nigerian militants beheaded five people in the city, a month suspected militants slit the throats of 15 Christians in the area.
"I see the hand of Boko Haram in that part of Cameroon, and that is worrying enough for us to mobilise," Hollande added.
Speculation is high that the kidnapping is in retaliation for the French intervention in Mali.
French gas group GDF Suez identified one of the captives as an employee. It was the first time Western tourists have been kidnapped in Cameroon.
On Sunday, another militant group in the area, Ansaru, said it had abducted seven people, including British, Italian, Greek and Lebanese workers, in Nigeria.