Human Rights Watch said abuses were committed by Malian forces and members of the ethnic Tuareg rebellion in the Kidal region, one of the last remaining rebel strongholds in the country.
The Malian government called for military support from former colonial power France to help fight Tuareg rebels and al-Qaida militants who seized territory in the aftermath of a 2012 coup.
An offensive began Wednesday to retake the Kidal region. Human Rights Watch said witnesses to the fighting suspected Malian forces were targeting men based largely on their ethnic background. Rebel forces, meanwhile, were suspected of using violence against the civilian population.
"The recent abuses by both sides and renewed fighting around Kidal underscores the urgent need for Malian soldiers and rebel combatants to respect the laws of war, minimize civilian harm, and ensure the humane treatment of detainees," senior West Africa researcher Corinne Dufka said in a statement from South Africa.
The U.S. State Department said this week it was monitoring the developments in Kidal. It said upcoming elections in July, however, would help ensure territorial integrity and sustainable peace.
The Malian government committed to July elections during an aid conference hosted last month by the European and French governments.