Mali's army has carried out a "series of summary executions" as it fights to recapture the Islamist-controlled north, a rights group has said.
The International Federation for Human Rights (FIDH) said some people were killed simply because they did not have identity documents.
A Malian army officer was quoted as denying the allegations.
Meanwhile, the UN says 7,100 civilians have fled to neighbouring states since 10 January to escape fighting.
Reports suggesting that the mainly black African Malian army, drawn largely from the south, has targeted Arabs and ethnic Tuaregs from the north expose a racial aspect to the war here which has been hidden by the emphasis on western troops fighting a war against Islamist insurgents, the BBC's Mark Doyle in Mali says.
France intervened militarily on 11 January to halt a militant advance.
It said al-Qaeda linked Islamists - some of whom were foreigners - threatened to turn Mali into a "terrorist state".
It has bombed suspected rebel positions and deployed about 2,000 troops to help the weak Malian army recapture territory.
FIDH said there needed to be an independent investigation into alleged abuses committed by Malian soldiers and those responsible should be punished.
In the garrison town of Sevare, at least seven people were executed at a military camp, near a bus station and a hospital, it said.
There was "credible information" pointing to 20 other executions in Sevare, with bodies "buried hastily, notably in wells", FIDH said.
Summary killings also took place in the towns of Mopti and Niono, the group added.
"Other allegations of summary executions continue to come from all areas of the west and centre of the country," it said.
It added that some of the victims were accused of possessing weapons, and of being "infiltrators" and "accomplices" of the militants.
Others were killed because they did not have identity documents or simply because of their ethnicity, FIDH said.
Dozens of ethnic Tuaregs in Mali's capital, Bamako, have also had their homes raided by troops, the group added.
The Malian army's Capt Modibo Traore said the allegations were "completely false" but declined to comment further, AP news agency reports.
United Nations refugee agency (UNHCR) regional coordinator Valentin Tapsoba said 7,100 people had fled to neighbouring countries in the last two weeks to escape fighting.
Most of them - some 4,000 - had fled to Mauritania, Mali's western neighbour, Mr Tapsoba told the BBC's Focus on Africa programme.
He said a further 3,100 people had crossed into Burkina Faso and Chad, to the east of Mali.
Nearly 10,000 have also also moved into camps inside Mali since 10 January, he said.
The latest conflict erupted after the militants advanced southwards, attacking the central towns of Konna, Diabaly and Douentza.
French officials say their forces have helped Malian troops to recapture all three towns.
France hopes to hand command of the operation to a West African force, which currently has some 1,000 soldiers on the ground.