Dozens of people have been executed by Mali's military in revenge killings in recent days, with corpses dumped in wells and left to decompose, human-rights activists say.
Many of the estimated 33 victims were killed simply because they lacked identity documents or because they were "light-skinned," according to a France-based group, the International Federation for Human Rights.
It was the latest report to heighten fears about Mali's notoriously ill-disciplined army, which has gained a free hand in some towns and villages because of its strong military support from France and a coalition of other countries, including Canada.
Western diplomats have been worried for months that Mali's army could begin to kill civilians under the cover of a Western military intervention. Now the murders seem to be mounting, according to several reports by human-rights groups.
French defence minister Jean-Yves Le Drian acknowledged on Wednesday that there was "a risk" that the Malian army had engaged in human-rights violations. "We must be extremely vigilant," he told the France 24 television channel.
France is counting on Mali's army leaders to "hold themselves responsible for avoiding any abuses," he added. "It is their honour that is at stake."
Revenge killings are said to be targeting specific ethnic groups in Mali – especially the northern-based Tuareg and Arab minorities – because they are often blamed for the rebellion that has split the country, with the north falling under the control of Islamist extremists. Most of Mali's soldiers are black Africans from the south of the country.
"These acts of revenge, together with the extreme tensions that exist between the communities, constitute an explosive cocktail leading us to fear that the worst could happen," federation president Souhayr Belhassen said in a statement on Wednesday.
The wave of revenge killings and other abuses began after French warplanes launched air strikes against Islamist insurgents two weeks ago, the human-rights federation said.
Most of the alleged killings were in or near the frontline towns of Sévaré, Mopti and Nioro, a few dozen kilometres from the scenes of clashes between Islamist insurgents and French-backed Malian troops. Most of the victims were "buried very hastily, in particular in the wells," the federation said.
It described how a Muslim cleric, Cheik Hama Alourou, was abducted by Malian soldiers in a village near Mopti, while a dozen Tuaregs had their homes looted by soldiers in Bamako, and summary executions were reported in other parts of western and central Mali.
Another group, Human Rights Watch, said its researchers had spoken to residents who saw a number of bodies thrown into a well in Sévaré. It cited witnesses who reported the execution of two Tuareg men by soldiers near Niono, and said it had credible information about sexual violence against women by soldiers in a village near Sévaré.
The Mali government has prohibited most journalists from travelling to Sévaré and Mopti, so the alleged abuses have been happening without any foreign witnesses. However, Reuters news agency reported Wednesday that one of its reporters had seen six bodies in Sévaré, including three bodies tossed down a well and three bodies, partly buried in sand, that seemed to have been burned.
The human-rights federation is calling for an independent investigation of the allegations. It noted that the Islamist insurgents have also been accused of a wide range of abuses.
Many witnesses say the Islamists have amputated the hands of suspected thieves, forced women to wear veils, and recruited hundreds of child soldiers. The International Criminal Court has launched an investigation into war crimes in northern Mali.