A kidnapped French family of seven has likely been separated into two groups by their abductors, France said Thursday, as Nigerian security forces combed restive border areas to find them.
The members of the family -- a couple, their children aged five, eight, 10 and 12 and an uncle -- were abducted while holidaying in the West African nation of Cameroon on Tuesday by six armed suspected Islamists on three motorbikes.
Cameroon officials said they were taken across the border into Nigeria, though Nigerian military spokesmen have so far only officially said they have been unable to confirm that information.
A Nigerian security official however said on condition of anonymity that searches were ongoing near the porous border with Cameroon in the country's northeast, a region on the edge of the Sahara where insurgents and criminal gangs have long operated.
French President Francois Hollande said in Paris that the family was probably being held in two groups.
"We are fully cooperating with Nigerian and Cameroonian authorities to find the location where our citizens are being held," Hollande told reporters.
He said the priority was to "first of all identify the exact place where (they) are being held, probably in two groups."
The hostages, on a visit to the Waza National Park in Cameroon at the time of the kidnapping, have been identified as Tanguy Moulin-Fournier and his wife Albane, as well as their four sons, Eloi, Andeol, Mael and Clarence.
Tanguy's brother Cyril Moulin-Fournier was with them at the time and was kidnapped as well. The three adults are all around 40 years old.
The Nigerian security official said "intelligence reports have shown that the abductors may be holding their victims ... around the Dikwa area," referring to a Nigerian town in the northeast.
"But I must tell you we haven't got the exact location. Our men and other sister security agencies, especially our colleagues in the immigration service, are already on operation and we have the strictest instruction to carry out the operation with caution."
Hopes for the family had been raised when a Cameroonian military source said earlier Thursday they had been found safe and well in Nigeria.
The source said they were found abandoned in a house in Dikwa, about 100 kilometres (60 miles) from the border with Cameroon.
France's Veteran Affairs Minister Kader Arif then confirmed that claim but later said he had merely passed on a media report. Cameroon's Communications Minister Issa Tchiroma Bakary bluntly stated that it was "a wild rumour".
-- An 'odious act' --
Hollande has condemned the seizure as an "odious" act, saying: "This is the first time that children have been taken hostage in this manner."
The French foreign ministry has urged citizens in the far north of Cameroon "to leave the area as quickly as possible" and advised against travel to areas bordering Nigeria until further notice.
It could not say how many French citizens are believed to be in the north but 6,200 in total are registered as living in Cameroon.
Foreign Minister Laurent Fabius said France would not give in to "terrorists," an apparent warning that a ransom would not be considered.
The defence ministry said a team of French gendarmes arrived in Cameroon on Tuesday to help with the probe, adding that they were being "protected by French soldiers".
French Defence Minister Jean-Yves Le Drian pointed the finger at Nigeria's Boko Haram extremist group but said it was not clear whether the kidnapping was linked to France's offensive against Islamist rebels in Mali.
"These are groups that claim the same fundamentalism, who use the same methods, whether it's in Mali, Somalia or Nigeria," he said.
Nigerian officials declined to comment on Boko Haram's alleged involvement.
While French officials have named Boko Haram as the likely culprits, a splinter faction of the group known as Ansaru, which has risen in prominence in recent weeks, appears to have prioritised Western hostages.
Ansaru claimed the December kidnapping of a French national in Nigeria's northern Katsina state and the abduction of seven foreigners from a construction site in the north's Bauchi state at the weekend.
In statements, Ansaru has protested France's efforts against Islamist rebels in Mali and warned of further attacks.