France will be increasing its West African force battling armed groups as part of efforts to back regional forces fighting Nigerian group Boko Haram, Jean-Yves Le Drian, France's defence minister said.

Le Drian said on Wednesday that the troops would provide support to forces fighting around Lake Chad, where Boko Haram has in recent months increasingly threatened Nigeria's neighbours. 

France has headquartered its more than 3,000-strong Sahel counter-insurgency force, Barkhane, in the Chadian capital N'Djamena, some 50km from the Nigerian border.

"We will slightly increase the numbers on Barkhane," Le Drian told reporters in Paris without giving specific details.

Cameroon, Chad, Niger and Benin have mobilised forces this year to help Nigeria defeat Boko Haram after it seized territory and staged cross-border attacks.

"We do not intend to take part in the fighting," Le Drian said.

Until now those troops have largely been tasked with tracking al Qaeda-linked fighters spanning across the Sahara from Mauritania in the west and southern Libya in the east.

France has, however, already sent about 40 military advisers to Niger's southern border with Nigeria to help coordinate military action by the regional powers fighting Boko Haram and has been operating
reconnaissance missions near the Nigerian border and sharing intelligence.

It is expected to reduce its 2,000 strong contingent in the Central African Republic to deploy more to Barkhane, defence and military sources have said.

France, which has the UN Security Council presidency, is also pushing for a resolution by early April that would back a 10,000-strong African force to fight Boko Haram, providing it crucial financing to carry out operations.