Chad's president says his country's troops are leaving Mali three months after the French-led mission to oust al-Qaida-linked militants began, raising concerns about the future of the war in the absence of the fierce Chadian desert fighters.

The drawdown of Chadian forces comes days after a suicide bombing killed three of their compatriots.

"Chad's army has no ability to face the kind of guerrilla fighting that is emerging in northern Mali. Our soldiers are going to return to Chad. They have accomplished their mission," Chad's president, Idriss Deby, said in an interview with French journalists posted online on Monday.

Deby said Chad had begun pulling out a battalion, with the rest of the 2,000 Chadian soldiers to return progressively, according to the joint interview with France's Le Monde newspaper, TV5 Monde and RFI radio. France has said it also wants to hand over responsibility for the mission to Malian and other African soldiers.

Chadian forces, trained in desert combat, have backed French forces in some of the heaviest battles during the war in northern Mali.

The Chadians have been especially instrumental in helping French troops in the mountains of the north Kidal region, where elements of al-Qaida in the Islamic Maghreb and other militants are hiding out after being ousted from major towns.

Their efforts have not come without cost: at least 23 Chadian soldiers were killed in one battle alone in February.

Deby held out the possibility that his country's troops could take part in an eventual UN force in Mali.

The French president, François Hollande, has said that about 2,000 French soldiers will still be in the former French colony by July, down from 4,000 at peak deployment, and at the end of the year 1,000 French soldiers will remain.

Mali fell into turmoil last March following a military coup in the capital, Bamako, which has long struggled to maintain control over the country's distant north, an area as large as Afghanistan.

The coup created a power vacuum that allowed fighters loyal to al-Qaida to invade the north, where they imposed their strict interpretation of sharia law, carrying out public executions, amputations and whippings.

France launched a military operation on 11 January after being asked to intervene by the country's interim president.

In the first weeks of the campaign, French and Malian forces easily took back cities in northern Mali, but jihadists remain in the desert, from where they have struck back.