BAMAKO, Mali (Reuters) -- A Tuareg-dominated rebel coalition said Saturday it was holding prisoner 19 Malian government soldiers captured in fighting a day earlier, amid growing violence in the north that threatens to derail peace efforts brokered by the United Nations. Army sources confirmed soldiers were missing after clashes late Friday that saw the Coordination of Movements of Azawad (CMA) briefly seize the small town of Tessit in northern Gao region of Mali. They declined to give further details.

A CMA representative said its fighters had withdrawn from Tessit by Saturday morning, taking with them captured ammunition and weapons, as well as the prisoners. “They are Malian soldiers, and there are 19 of them,” Almou Ag Mohamed told Reuters.

Photographs seen by Reuters that were provided by a CMA fighter involved in the fighting in Tessit showed at least a dozen men, most in civilian clothing, with their hands tied behind their backs and surrounded by rebel fighters. It was not immediately possible to independently authenticate the images or identify the captives further.

A ceasefire deal was signed between the government, its allies and northern separatist groups last year, but violations of the agreement have increased since pro-government fighters seized the flashpoint town of Menaka last month.

“There was fighting between the CMA and the army yesterday around dusk in Tessit. Some soldiers are missing. It’s very likely that they were taken prisoner,” said an army officer who is based in the nearby town of Gao and requested anonymity.

An army intelligence officer in the capital Bamako also said government soldiers were missing, but would not say how many.

The violence has continued in northern Mali despite a 2013 French-led intervention that pushed back al Qaeda-linked fighters who hijacked a Tuareg-led uprising and seized two-thirds of the country in 2012.

Western powers hope an agreement negotiated in Algeria between the government and the rebels will end decades of northern rebellions and allow international and Malian forces to concentrate on defeating Islamist militants.

However, most rebel groups boycotted the signing of the peace deal last week and have given it only initial approval.