Francois Hollande, the French president, pointed the finger at al-Qaeda allied fundamentalist group Boko Haram, based in neighbouring Nigeria, blaming them for the kidnapping Tuesday.
The seven hostages were taken from Cameroon’s far north close to the Waza National Park and Lake Chad, both attractions for tourists on adventure holidays. The semi-arid area lies alongside the border with Nigeria, and Islamist strongholds in towns there, including Maiduguri, are less than 100 miles to the west.
It is nonetheless believed to be the first time that Nigeria’s growing problem with Islamic fundamentalism, and kidnapping, has been exported into its generally stable neighbour.
“They have been taken by a terrorist group that we know and that is in Nigeria,” Mr Hollande told reporters during a visit to Greece.
He added: “I see the hand of Boko Haram in that part of Cameroon.”
Issa Tchiroma Bakary, Cameroon’s information minister, said his government and security services were investigating the reports but would not immediately confirm details.
One of the adults is employed by GDF Suez. The French utility giant said the employee, based in the Cameroon capital Yaounde, and the family were on holiday in the north of the country.
A Western diplomat in the region told AFP that six armed kidnappers on three motorbikes abducted a couple, their four children and an uncle in the northern village of Dabanga near the Nigerian border.
The children are aged five, eight, 10 and 12, the diplomat said.
Mr Hollande said that his intelligence services said they suspected the group was being taken towards northern Nigeria, or had already been smuggled across the border.
A French engineer was kidnapped close to Katsina, a Nigerian town further west, in December. Eight other French nationals, mostly employees with its uranium miner Areva, have been held hostage in the region since 2010.
Seven other Westerners, including a British construction specialist, were kidnapped on Sunday from another northern Nigerian town.
The French president is facing increasing domestic pressure to justify ordering the operation in Mali, where 4,000 French troops helped stall an Islamist surge south towards the capital last month.
“France is in Mali, and it will continue until its mission is completed,” Mr Hollande said.