Dozens of people have been killed in a car bombing at a military camp in the northern city of Gao in Mali. The area houses government soldiers and rival armed groups who conduct mixed patrols under a UN-brokered peace deal aimed at curbing violence in the region.

Wednesday morning's explosion hit the Joint Operational Mechanism base in Gao, which was seized by armed groups in 2012 before French forces drove them out a year later. Specifically, former rebels from the Tuareg-led CMA movement were preparing to go on a joint patrol with pro-government militia members, under the terms of the 2015 agreement, when the attackers struck.

President Ibrahim Boubacar Keita declared a three-day mourning period following the attack, the worst in years. 

"Some have died from their wounds, and others are in a very grave state," he said. "At this point, it's not the toll of dead and injured that interests me, it's saving who I can."

The provisional toll is "47 dead and several injured", according to state TV broadcaster ORTM. Earlier, a hospital source in Gao said at least 40 people had died and 60 were hurt.

Abdoulaye Idrissa Maiga, Mali's defence minister, was to fly to Gao later on Wednesday.