By Tansa Musa and Bate Felix
YAOUNDE/DAKAR, Feb 20 (Reuters) - The Islamist militants believed to have abducted a French family of seven, including four children, in Cameroon have taken them into Nigeria, a Cameroonian minister said on Wednesday.
The abduction highlights the growing risk of attacks on French nationals and interests in Africa since Paris sent forces into Mali to oust Islamist rebels occupying the country's north.
Speaking on French television, Joseph Dion Ngute, a junior minister at the foreign ministry, said the kidnappers had put the hostages on motorcycles after their car broke down.
"They then took another woman hostage with her car and fled into Nigeria," he said. "Our forces and the Nigerian forces were alerted, but before they reacted the kidnappers had vanished."
It was not clear what had happened to the additional female hostage.
Security in the Dabanga area, 10 km (six miles) from the Nigerian border, where they were taken has been reinforced and "urgent measures" to locate the family put in place, he said.
It is the first case of foreigners being seized in the mostly Muslim north of Cameroon, a former French colony. But the region - like others in West and North Africa with typically porous borders - is considered to be within the operational sphere of Nigerian Islamist militants Boko Haram and Ansaru.
The father of the family, which included four children aged between 5 and 12, worked for utility firm GDF Suez. French television reported the father was from a family of winemakers in the Burgundy region.
Nigerian army spokesman Colonel Sagir Musa said "the armed forces were on alert ... ready to apprehend any criminal elements or terrorist that come into our areas."
He gave no further details.
Cameroon state television said a French military unit had arrived in the country to help in the rescue efforts. A French defence ministry spokesman said the report was "baseless".
"Based on long-standing and political and socio-economic ties between France and Cameroon, it is expected that French forces will engage in resolving this issue from within Cameroonian borders, with the support of the Cameroon government," said Nadia Ahidjo of africapractice, an Africa-focused consulting firm.
"TERROR BREEDS TERROR"
France has about 6,000 nationals in Cameroon. It issued a travel warning on Tuesday advising its citizens not to travel to the extreme north of Cameroon and those already in that region to 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.
French Defence Minister Jean-Yves Le Drian said on Wednesday all the evidence pointed to Boko Haram, but there did not appear to be a direct link with France's intervention in Mali.
"We believe it's the Boko Haram group that carried out the kidnapping, but we don't know for sure. Unfortunately, terror breeds terror," Le Drian told France 2 television.
Boko Haram pose a big threat to stability in Nigeria, Africa's top oil-producing state. Western governments worry they could link up with other Islamist groups in the region.
France intervened in Mali last month after Islamist rebels seized control of the north of the country and pushed south towards the capital Bamako.
French-led forces have since driven the Islamists from north Mali towns and back into remote desert and mountains.
"It's these groups that are calling for the same fundamentalism, whether it's in Mali or in Somalia or in Nigeria. These groups threaten our security," Le Drian said.
French President Francois Hollande said the kidnappings would not stop France from pursuing its operation in Mali.
The kidnapping of the family brought the number of French hostages held hostage in isolated regions of west and north Africa to 15, including one abducted by Nigerian al Qaeda-linked Ansaru in December. (Additional reporting by John Irish in Dakar, Alexandria Sage in Paris and Joe Brock in Abuja; writing by John Irish; editing by Mark Heinrich)