Fighting between rival Tuareg factions has intensified and threatens to derail a 2015 peace deal meant to end years of conflict and instability in the landlocked West African nation, a major gold producer.

The rebel Coordination of Azawad Movements (CMA) and the pro-government Gatia are locked in a bitter power struggle in northern Mali, despite the return of state authority to its cities in March for the first time since a 2012 Tuareg uprising.

"Anefis has been under the control of the CMA since yesterday. Preparations are being made to retake it," Ahamoudane Ag Ikmasse, a Gatia-allied local lawmaker in the nearby major city of Kidal told Reuters by telephone.

CMA spokesman Redouane Ag Mohamed Ali confirmed that Anefis, a town in the Sahara desert, had been taken.

"It was a CMA position that was retaken by Gatia in 2015. CMA now controls all of the Kidal region," he said, although Ag Ikmasse disputed that.

Northern Mali was once a thriving tourist hub owing to its fabled history of caravan routes, gold and medieval Islamic scholarship.

But a Tuareg insurrection in 2012 created a power vacuum that has turned it into a launchpad for jihadi attacks across the Sahara and the Sahel to the south.

Former colonial master France intervened a year later to push the Islamists back, but they have struggled to stabilize Mali.

African powers backed by France launched a multinational military force this month, primarily to tackle Islamist militants across the region, which is seen as forming the basis of an eventual exit strategy for around 4,000 French troops now deployed there.