Three Malian soldiers have been wounded in the first clashes with Tuareg rebels since the two sides signed a ceasefire deal in June, the army has said,
A Malian capitain warned the clash could endanger the truce.
The fighting took place near the western town of Lere and comes a week after President Ibrahim Boubacar Keita was sworn in, highlighting simmering tensions as he seeks to secure an end to cycles of uprisings by northern rebels.
The Tuareg rebels have picked up arms thrice since independence in 1960, but it was only last year that they succeeded in making significant gains. They were temporarily sidelined by radicals operating in the area, though they have grown in strength again since French-led forces drove out the al-Qaeda linked fighters from the region.
A UN peacekeeping mission is now rolling out to ensure stability as French troops gradually withdraw.
"An army patrol came across some gunmen in four-wheel drives. They refused to follow the army's orders and opened fire on the troops," said army spokesman Captain Modibo Naman Traore.
Attaye Ag Mohamed, one of the founders of the Tuareg rebellion, accused the army of starting the fighting by surrounding their position.
In June, the rebels signed an agreement mediated by the president of Burkina Faso, agreeing to a ceasefire in order to allow Mali's presidential election to go ahead on July 28. The rebels also agreed to garrison their fighters, but the insurgents were frequently spotted outside their assigned bases in the northern province of Kidal.
Talks are to begin later this year between the government and the rebels. However, the idea of negotiating with them remains deeply unpopular in southern Mali.