UN peacekeepers said they would establish a 20-kilometre "security zone" around the town of Kidal in restive northern Mali with effect from Tuesday following deadly clashes between a pro-government group and Tuareg rebels.
The fighting erupted Monday at Agnefis, about 120 kilometres south of the strategic town of Kidal, "killing several people", a regional security source said.
The UN peacekeeping mission in Mali known as MINUSMA said in a statement it was a "blatant violation" of the recently agreed Mali peace deal known as the Algiers Accord.
"The international community, as well as the population, is concerned by the increasing number of these violations, which could hinder the progress made towards a stable and lasting peace in Mali," it said.
A MINUSMA security source told AFP the clashes had left "at least 10 dead and many injured".
Fahad Ag Almahmoud, a top official from the pro-government Imghad Tuareg group spoke of 15 deaths, including those of some military leaders from the main Tuareg rebel group CMA or Coordination of Movements for Azawad.
"The situation has stabilised. The fighting has temporarily stopped," Ag Almahmoud said Monday afternoon.
The CMA meanwhile confirmed the clashes but did not provide a toll.
"We are very worried about the future, especially because it seems both sides are using heavy weaponry," a foreign security source in the region told AFP.
The same source said that during Mali's rainy season, many of the roads become impassable in the north and groups end up fighting each other for control of roads used for trafficking.
The UN peacekeepers said they were declaring a security zone around Kidal "to avoid any possible extension of the fighting that could affect the population" of the town.
The zone would come into force from 0800 GMT Tuesday and "remain until further notice".
Any movement within the zone by pro-government Tuareg forces or their allies "will be deemed to constitute an imminent danger to the security of the population of the town of Kidal", it said, stressing that the peacekeeping force would "act in accordance with its mandate" in the event of any violation.
MINUSMA also said it would carry out investigations to determine responsibility for the ceasefire violation and forward the findings to the UN Security Council.
The two groups accused each other of starting the fighting over the weekend, breaching a peace deal signed by the governmental camp on May 15 and the rebels on June 20.
Mali was shaken by a coup in 2012 that cleared the way for Tuareg separatists to seize towns and cities of the north, an expanse of desert the size of Texas.
Al-Qaeda-linked militants then overpowered the Tuareg, taking control of the region for nearly 10 months until they were ousted in a French-led military offensive.