A suicide attack in the disputed north Malian town of Tabankort killed at least five people overnight, according to two Tuareg rebel sources on Wednesday.
A source for the main Tuareg rebel group MNLA said that multiple suicide bombers from a rival, pro-government militia attacked their positions, killing 13 people. A second source said that five separatist fighters had been killed.
Fighting between rival armed groups vying to control Tabankort has broken out several times this month, prompting the UN peacekeeping mission MINUSMA to carry out air strikes on Tuareg rebel forces.
The incident, which separatists called a violation of a ceasefire deal, threatens to derail upcoming peace talks in Algiers over the future of northern Mali.
The weak Bamako government is struggling to restore its authority on northern zones where a medley of armed groups operate as well as al-Qaeda-linked Islamists who briefly occupied the region in 2012.
In a sign of high tensions, witnesses said that UN peacekeepers on Tuesday had fired lived rounds at demonstrators protesting against a new disarmament plan, killing three.
MINUSMA said they were only warning shots and it would launch an inquiry.