France will boost its military presence in the troubled Sahel region of Africa where jihadist groups operate to support the fight against Boko Haram, Defence Minister Jean-Yves Le Drian said Wednesday.

Speaking to reporters, he said France would "slightly increase" the number of soldiers operating under its Barkhane anti-jihadist operation in the Sahel and reduce armed forces in the Central African Republic "to give us the means to support" the fight against Boko Haram.

Under Barkhane, France already has some 3,000 troops in the region but Paris has insisted it will limit itself to "indirect support" of the widening African effort to combat the growing Boko Haram insurgency.

The radical Islamist group has recently spread its insurgency beyond Nigeria to neighbours Chad and Niger, in addition to further attacks in Cameroon, and those countries have been drawn into the battle to stop the extremists.

Le Drian, who gave no specific troop figures, reiterated Wednesday that Paris had no desire to get dragged into fighting, adding it would continue to provide logistical support and intelligence.

"What is reassuring on Boko Haram is that there is a real will from the countries involved to organise themselves and lead the fight," Le Drian said.

"That's a new element that we appreciate."

Le Drian added that the Madama desert base being built in northern Niger to combat the growing flow of weapons and jihadists from neighbouring Libya to hot spots in countries such as Mali or Nigeria would be "fully operational" in July.

In the Central African Republic, where it intervened in December 2013 to try and contain a deadly sectarian conflict, Paris has already started to reduce its troop numbers as it gradually hands over to a 8,500-strong UN peacekeeping force.

By the end of the year, there should be fewer than 1,000 French forces in the country, compared to 2,600 at the height of France's presence there.