A suicide attack has left two Chadian troops from the UN peacekeeping mission and a civilian dead in northern Mali, a UN spokesman said.

A bomber exploded himself up in an explosive-laden vehicle at a checkpoint at the entry to the town of Tessalit on Wednesday, wounding six others.

The unnamed military source told AFP news agency that the number of attackers was higher.

"Jihadists attacked the positions of the Chadian army in Tessalit with heavy arms and car bombs. Two Chadian troops have been killed. The four suicide bombers were also killed on the spot and a civilian also died," the source told AFP.

No group has claimed the attack.

Earlier violence

Northern Mali fell to various rebel groups following a March 2012 coup.

A French-led military intervention launched in January drove the rebels out of major towns, but top UN envoy Albert

Koenders warned earlier this month that attacks in the past month were a "wake up call'' highlighting the challenge of restoring security.

France keeps 3,000 troops in its former colony out of a contingent it dispatched in January, but Paris plans to draw down the force to 1,000 men by the end of January next year.

The 2,000 Chadian soldiers of the African-led International Support Mission in Mali (AFISMA) were at the forefront of the operation, losing at least 38 men in battle.

The UN peacekeeping force, expected to reach a strength of 12,600, replaced AFISMA in July.