A pro-government militia seized key positions in northern Mali on Monday from separatist rebels, security sources said, breaking a fragile ceasefire in the restive region.

The Imghad and Allies Tuareg Self-Defence Group (GATIA) took over parts of the desert town of Menaka from fleeing rebel fighters, also Tuareg, a United Nations security source said.

The main Tuareg rebel alliance, known as the Coordination for the Movements of Azawad (CMA), denounced the action as "even more unacceptable given that it comes after a final commitment of the CMA" to sign an accord for peace in northern Mali.