Boko Haram fighters have overrun an army base in the remote northeast Nigerian town of Baga, killing scores of soldiers in the attack, security sources have said.

Baga is known for hosting the headquarters of a multinational force comprising troops from Niger, Nigeria, Chad and Cameroon, although only Nigerian troops are actually stationed there.

Troops eventually fled the remote station on the semi-desert shores of Lake Chad after it was attacked on Saturday by Boko Haram fighters using military vehicles, two sources said.

Earlier on Friday, suspected members of the armed group raided the northeast village of Malari, kidnapping about 40 boys and young men.

The fighters came to the remote village of Malari and urged people to come out and listen to a sermon, farmer Bulama Malam told reporters on Saturday.

"After telling us that they wanted to preach to us, they began to select young men aged between 12 and 25,'' Malam said. "I was lucky to escape because they only selected very young and able-bodied men."

He spoke in Maiduguri, the capital of northeast Borno state, to which he escaped on foot.

Nigeria''s longstanding conflict with Boko Haram has killed over 10,000 people this year, according to a count by the Council on Foreign Relations in November.

Neighbouring countries threatened

It is the gravest threat to Nigeria, Africa's biggest economy, and a headache for President Goodluck Jonathan ahead of an election on February 14 where he is being challenged by opposition leader Muhammadu Buhari, a former military ruler seen as tough on security.

After beginning their fight for an Islamic state five years ago in the northeastern city of Maiduguri, the group has radiated outwards into porous border areas, threatening Nigeria's neighbours around the Lake Chad Basin.

In northern Cameroon, at least 15 people died in an attack by suspected Boko Haram fighters on a bus, officials said on Saturday.

Cameroon's army has been trying to dislodge the fighters from its Far North region with the help of air strikes.

Nigerian Interior Minister Hassoumi Massaoudou said late last month that his country was ready to negotiate with Boko Haram, but did not even know who in the group to talk to.

Baga came into the international spotlight early in 2013, when dozens of people, mostly civilians, were killed in fighting between the multinational force and Boko Haram. Many were burned alive in their thatched houses.