At least 53 people died in western Ethiopia after an unidentified armed group attacked a civilian convoy and its military escort in a region plagued by ethnic violence, a rights body appointed by the government said on Sunday.
The previously unreported attack occurred on March 2 in Metekel, in the Benishangul-Gumuz region, the Ethiopian Human Rights Commission said.
Twenty soldiers and three civilians were killed in the ambush, while 30 attackers died during the day-long gun battle that followed.
Eleven more people were killed the following day - including one who was burned alive - as security forces rounded up suspects and carried out summary killings, according to the rights group.
The commission investigated the incident after a video posted on social media on Friday showed armed men, some in military uniforms, using a stick to poke a man back onto a burning pile of bodies after he tried to escape. The government said on Saturday it would act against the perpetrators.
According to the commission, the government soldiers stopped a bus, pulled out eight ethnic Tigrayan civilians who had just been released from prison and accused them of orchestrating the attack.
Security officers detained and beat the men, then they shot them, along with two men from the local Gumuz ethnic group, and burned their bodies, the commission said. Security officers told the commission that they found cash and a satellite phone with the Tigrayan suspects.
Security forces discovered another Tigrayan man hiding in a car, tied him up and threw him onto the pyre, the commission said, noting the presence of Ethiopian soldiers and uniformed forces from the Amhara region and Southern Nations Nationalities and Peoples' Region.
The rights body did not say which security force killed the civilians.
Spokesmen for the two regions were not available for comment. A military spokesman and government spokesman did not immediately respond to requests for comment.
The violence in the Benishangul-Gumuz, home to several ethnic groups, is separate from the war in Tigray, a northern region that has been fighting central government rule for more than 16 months.
The United Nations has said at least 15,000 Tigrayan civilians were arrested or detained in connection with a state of emergency declared in November and lifted last month.