Rights campaigners on Wednesday denounced pro-government forces' killing of six civilians in northern Mali, including an aid worker for a European charity, as a "war crime".
The United Nations announced on May 22 it was sending investigators to Tin Hama, a town in the northeastern region of Gao, after being alerted to "serious violations of human rights... including the execution of a number of civilians".
The government has rejected accusations that the army was involved, describing the alleged atrocity as "a bloody settling of scores between armed groups".
The International Federation for Human Rights and Malian Association of Human Rights said the victims were murdered following clashes between the main country's main Tuareg-led rebel alliance, known as the CMA, and the pro-government Imghad and Allies Tuareg Self-Defence Group (GATIA), the rights groups said in a joint statement.
"Some of these deaths were summary executions and extra-judicial killings of civilians which therefore constitute war crimes whose perpetrators should be prosecuted by Malian courts and possibly the International Criminal Court," the statement said.
The rights groups received confirmation that six civilians were killed, the statement added.
The campaigners said the fighting had displaced around 30 families, mostly from the ethnic-Tuareg Kel Essouk tribe.
The Siwel online news portal, which describes itself as an Algerian Tuareg website, published a "testimony of the victims' families" which said the killings came after GATIA had tried in April to recruit inhabitants of Tin Hama.
GATIA's overtures were rejected by the town's Kel Essouk people, but members of another Tuareg tribe, the Idourfane, agreed to join, according to the testimony.
The account, which could not be independently verified, said two civilians were killed as the CMA attacked pro-government positions in Tin Hama on May 20.
After the CMA withdrew, armed men including GATIA fighters summoned a Kel Essouk leader and ordered him to leave with the entire community by the following morning, according to the testimony.
The fighters seized six youths from the community the following morning, including a 13-year-old boy and an employee of Action Against Hunger Spain, it said.
They were taken to a pond where they were beaten, "tied up with their turbans" and gunned down with automatic weapons, the testimony said, adding that the killing sparked an exodus of Kel Essouk to neighbouring Niger.
Renewed fighting over the last month in northern Mali between rebel groups and loyalist fighters has led to the displacement of 57,000 people fleeing violence or forced recruitment, according to the UN's refugee agency.
There are now 100,000 people internally displaced in the impoverished west African nation's northern desert, the UNHCR announced on May 29.