The UN anti-genocide envoy says he is 'deeply disturbed' by reports of reprisal attacks by Malian troops as they retake control of the north.
The abuse could 'constitute atrocity crimes', Adama Dieng said in a statement.
Reports suggest that Malian soldiers, mainly from the south, are targeting Arab and ethnic Tuareg civilians in frontline towns.
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Adama Dieng, the UN's special adviser on the prevention of genocide, said the allegations included summary killings and disappearances in Sevare, Mopti, Niono and other towns close to the areas where fighting was occurring.
There had also been reports of mob lynching and stealing of properties belonging to Arab and Tuareg communities, he added.
"While the liberation of towns once under the control of the rebel and extremist groups has brought hope to the populations of northern Mali, I am deeply concerned at the risk of reprisal attacks against ethnic Tuareg and Arab civilians," Mr Dieng said.
"Targeting of ethnic or religious groups in an armed conflict, and if such abuses are carried out in a widespread and systematic way, could constitute atrocity crimes."
Mr Dieng said the Malian army had a responsibility to "protect all populations, irrespective of their race or ethnicity".
He expressed particular concern over reports that the armed forces were recruiting and arming proxy militia groups to carry out attacks against Arab and Tuareg communities.
Mr Dieng welcomed the decision of the International Criminal Court (ICC) to investigate the situation in Mali.
HOLLANDE SET TO VISIT MALI
The comments came ahead of France's President Francois Hollande's visit Mali to express his support for French troops fighting in the former colony and to push for their speedy replacement by African forces.
"I am going to Mali to express to our soldiers all our support, encouragement and pride," Hollande said Friday after the announcement of his visit.
"I'm also going to ensure that African forces come and join us as quickly as possible and to tell them we need them for this international force."
Hollande will be accompanied by Foreign Minister Laurent Fabius, Defence Minister Jean-Yves Le Drian and Development Minister Pascal Canin.
The trip follows a three-week military intervention in the former colony in which French forces have recaptured large areas of northern Mali from Islamist groups.
Hollande will travel first to Timbuktu, where according to the Malian presidency he will meet with troops and visit the 700-year-old mud mosque of Djingareyber, a UNESCO World Heritage site, and the Ahmed Baba library, where Islamists burned priceless ancient manuscripts before fleeing.
Hollande and interim Malian president Dioncounde Traore, who will visit Timbuktu together, will then travel to the capital Bamako for a working lunch, Traore's office said on Twitter.
