YAOUNDE/DAKAR (Reuters) - Islamist militants from neighbouring Nigeria abducted a French family of seven, including four children, in northern Cameroon on Tuesday, French President Francois Hollande said.
The risk of attacks on French nationals and interests in Africa has risen since France sent forces into Mali last month to help oust Islamist rebels occupying the country's north.
"They (French family) have been taken by a terrorist group that we know and that is in Nigeria," Hollande told reporters during a visit to Greece.
The men on motorcycles, armed with Kalashnikovs, intercepted the family in their car at 7:00 a.m. British time and forced them to drive to the nearby Nigerian border, an aide to the governor of the province told Reuters. The four-wheel-drive vehicle was later found abandoned.
Islamist radicals in northern Nigeria now pose the biggest threat to stability in Africa's top oil-producing state.
Western governments are concerned that Nigeria's Boko Haram Islamists may link up with groups elsewhere in a region with poorly secured borders, especially al Qaeda's North African wing AQIM given the conflict in nearby Mali.
The seven French nationals were abducted in Dabanga about 10 km (six miles) from the Nigerian border near the Waza national park, where they had spent the night in the extreme north of Cameroon, an area where Westerners often go for holidays.
The parents of the family, which included two boys and two girls as well as another relative, worked for French utility firm GDF Suez.
GDF, which is building a liquefied natural gas project in south Cameroon, confirmed one of its employees and his family had been kidnapped while on holiday.
Cameroon state radio reported that witnesses said the three adults had been separated from the four children and Cameroonian defence forces had been deployed to the area.
It was the first case of foreigners being seized in the mostly Muslim north of Cameroon, a former French colony.
"I see the hand of Boko Haram in that part of Cameroon. France is in Mali, and it will continue until its mission is completed," Hollande said.
France intervened in Mali last month when Islamist rebels, after hijacking a rebellion by ethnic Tuareg MNLA separatists to seize control of the north in the confusion following a military coup, pushed south towards the capital Bamako.
Eight French citizens are already being held in West Africa's Sahel region by al Qaeda-affiliated groups.
"It shows that the fight against terrorist groups is a necessity as they threaten all of Africa," French foreign minister Laurent Fabius told reporters.
"I think there is a terrorist threat in much of West Africa, as far as Cameroon," Fabius said.
France's foreign ministry issued a travel warning on Tuesday advising its nationals not to travel to the extreme north region of Cameroon and those already there should take precautionary measures and leave as soon as possible.
Cameroon is a largely secular state where 70 percent of the population is Christian and about 24 percent moderate Muslim. Most Cameroon Muslims live in the three northern regions of the country. Until now, there have been no known links between Muslims in north Cameroon and Islamists in northern Nigeria.
Most kidnappings of Western nationals in the region have been committed by pirates operating off Cameroon's southern Bakassi peninsula and the Gulf of Guinea, though the French foreign ministry advises against all travel in the north.
Charles Gurdon, managing director of Menas Associates, a London-based risk analysis consultancy, said there had been growing concerns over a possible spill over from Nigeria into the north of Cameroon.
"Traces of ... Boko Haram had been discovered (in Cameroon), but the Cameroon government has been covertly trying to undermine the threat," he said.
On Sunday, seven foreigners were snatched from the compound of Lebanese construction company Setraco in northern Nigeria's Bauchi state, and al Qaeda-linked Ansaru took responsibility.
Northern Nigeria is increasingly afflicted by attacks and kidnappings by Islamist militants. Ansaru, which rose to prominence only in recent months, has also claimed the abduction in December of a French national who is still missing.
Ansaru said the abductions were driven by "the atrocities done to the religion of Allah by the European countries in many places, such as Afghanistan and Mali."
Ansaru is thought to have loose ties to Boko Haram, which has killed hundreds during a three-year-long insurgency focused mostly on the security forces, religious targets and politicians, rather than foreigners.
Additional reporting by John Irish and Diadie Ba in Dakar, Jean-Baptiste Vey in Athens, Vicky Buffery, Alexandria Sage, Marion Douet and Muriel Boselli in Paris; Writing by John Irish and Bate Felix; Editing by Michael Roddy