Eight Malian soldiers were killed Monday in the country's restive desert in an ambush by fighters from the west African nation's main Tuareg-led rebel alliance, humanitarian and security sources said.

The attack comes against the backdrop of an upsurge in violence in northern Mali which United Nations peacekeepers have warned is threatening a peace accord between the rebels and government due to be signed on Friday in Bamako.

"During an ambush of the Malian army by the rebel Coordination of Azawad Movements (CMA) between Timbuktu and Goundam on Monday morning, eight Malian soldiers were killed and several wounded," an official from a charity in the area said.

The source said two Malian army vehicles had also been set on fire while the rebels lost one of their vehicles.

The Malian army refused to comment officially but a military source linked to reinforcements sent to the scene confirmed the information.

"We have eight dead and 10 wounded, and soldiers who are missing for the time being," the source said, adding that it was not yet clear if the CMA had sustained casualties.

A Timbuktu-based military source from MINUSMA, the UN peacekeeping mission in Mali, told AFP the rebels had waited in four vehicles for the troops, who were due to take over a patrol.

"This is a carefully prepared ambush," the source said.

A CMA leader told AFP the rebel movement had "ambushed the Malian military" and that "the death toll was not yet known".

MINUSMA chief Mongi Hamdi was quoted in a statement from the force as saying he "condemns in the strongest terms" the ambush, which he said was in violation of ceasefire agreements.

Tuareg rebel groups have been clashing with Malian forces and pro-government militias in the north since the end of April.

Monday's attack came less than a week after a soldier was killed along with ten rebels during a gun battle in the central market town of Tenenkou.

The MINUSMA statement did not give the number of troops killed but Hamdi called for an end to the violence and urged "all parties to demonstrate their commitment on the ground to the process leading to the signing of a peace agreement on May 15".

The UN Security Council has also demanded an immediate halt to the fighting and threatened to impose sanctions against those responsible, warning that the bloodshed threatened to undermine the peace process.

The Malian government and a coalition of armed groups known as the Platform have initialled the peace accord, brokered by Algeria under UN auspices.

The recent violence comes amid assurances by the CMA that it was committed to the deal brokered by Algeria and due to be ratified at the Bamako ceremony.

Meanwhile the People's Alliance for Peace and National Unity (ALPPUNA), a pressure group of mainly Arabs from the north, announced the creation of a military wing on Monday.

"The ALPPUNA informs the national and international community of its decision to create its own armed wing to ensure the legitimate defence of populations and their property," it said in a statement.

"This decision is justified by the extreme seriousness of the repeated attacks against peaceful citizens in the Timbuktu region," the statement went on, adding that the group wanted peace.