Mali's prime minister said his country was at war with Tuareg separatists after the rebels attacked a northern town he was visiting, killing soldiers and abducting around 30 civil servants.
Some shooting had already broken out before Prime Minister Moussa Mara arrival in Kidal early on Saturday and he was forced to take shelter in an army base as rebel fighters attacked and seized the regional governor's office.
Clashes continued throughout the day with sporadic shooting eventually easing during the night.
"In light of this declaration of war, the Republic of Mali is henceforth at war," Mara told a Reuters reporter inside the base overnight.
"We are going to formulate the appropriate response to the situation," added the prime minister, who was visiting Kidal for the first time since his appointment last month to revive long-delayed talks with northern armed groups.
Mali, a former French colony, was thrown into turmoil in 2012 when al Qaeda-linked Islamists took advantage of a Tuareg-led rebellion and seized control of the country's north.
A French-led military operation, known as Serval, drove back the Islamists last year but now the Mali government's focus has turned back to the Tuareg rebels.
A spokesman for the MNLA rebel group claimed control of the town of Kidal on Sunday. During the day Mara moved on from Kidal to another northern town, Gao.
At least one soldier was killed and 23 others were wounded in the clashes which now threaten to sink efforts to find a peaceful solution to long cycle of rebellions in the West African nation's desert north.
MINUSMA, a nearly 13,000-strong United Nations peace-keeping mission, is rolling out but is not yet at full strength.
Mara poured criticism on both the French and U.N. forces for allowing the attack to take place.
"You were witnesses today to the more than passiveness of these forces," he said. "The very least we'd expected from MINUSMA and Serval was that they'd ensure the governor's office wasn't attacked."
A U.N. spokesman on Sunday declined to comment on the events in Kidal.
REUTERS