France on Wednesday urged its citizens to leave northern Cameroon after seven members of a French family were seized in a kidnapping officials suspect was carried out by Nigerian Islamist group Boko Haram.
The family -- a couple, their children aged five, eight, 10 and 12 and an uncle -- were snatched in northern Cameroon by six gunmen on three motorbikes on Tuesday and officials said they had been taken across the border into Nigeria.
With the latest abduction, France has overtaken the United States as the country with the most number of hostages held abroad, with 15 nationals in captivity against nine Americans.
President Francois Hollande condemned the seizure as an "odious" act, saying: "This is the first time that children have been taken hostage in this manner."
"We are doing everything with the help of authorities in Cameroon and Nigeria to find our compatriots," government spokeswoman Najat Vallaud-Belkacem quoted Hollande as telling a cabinet meeting.
The French foreign ministry in a notice urged citizens in the far north "to leave the area as quickly as possible" and advised against travel to areas bordering Nigeria until further notice.
Foreign Minister Laurent Fabius said France would not give in to "terrorists," a seeming allusion that ransom will not be considered.
"We must do the maximum (to free the hostages) but nothing would be worse than yielding. We will not yield to terrorist groups," he told the National Assembly.
"This adds to the other hostage-takings. Sadly France is one the countries that is perhaps most affected by this," he said.
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 authorities have launched a preliminary investigation into the "kidnapping staged by a terrorist organisation," a judicial source said. Such cases are routinely opened when crimes are committed against French citizens abroad.
The ministry 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.
French Defence Minister Jean-Yves Le Drian pointed the finger at Boko Haram but said it was not clear whether the kidnapping was linked to France's intervention against Islamist rebels in Mali.
"We believe that the Boko Haram sect carried out this kidnapping, but we don't yet have a claim of responsibility," Le Drian told France 2 television.
"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 have declined to comment on Boko Haram's alleged involvement.
Spokeswoman Marilyn Ogar of the country's main intelligence branch, the State Security Service, told journalists it was "premature" to discuss the kidnapping, citing security concerns.
President Goodluck Jonathan's spokesman Reuben Abati said he needed to "check with the security services" before commenting on the incident.
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.