A local youth group aided by police and militia killed at least 600 people in a "rampage" on November 9 in Ethiopia's northern Tigray region, the national rights watchdog said Tuesday.
The massacre in the town of Mai-Kadra is the worst-known attack on civilians during Ethiopia's ongoing internal conflict pitting federal forces against leaders of Tigray's ruling party, the Tigray People's Liberation Front (TPLF).
Amnesty International previously reported that "scores, and likely hundreds, of people were stabbed or hacked to death" in the November 9 attack in Mai-Kadra.
But Tuesday's report from the Ethiopian Human Rights Commission (EHRC) provides a more detailed account, accusing the Tigrayan youth group known as "Samri" of targeting non-Tigrayan seasonal labourers working on sesame and sorghum farms in the area.
The EHRC is a government-affiliated but independent body whose chief commissioner, Daniel Bekele, was appointed by Prime Minister Abiy Ahmed.
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The perpetrators "killed hundreds of people, beating them with batons/sticks, stabbing them with knives, machetes and hatchets and strangling them with ropes. They also looted and destroyed properties," the report said.
The attack "may amount to crimes against humanity and war crimes," it said.
Sources including eyewitnesses and members of a committee formed to bury the dead "estimate a minimum of 600 have been killed and say the number is likely to be higher still," the report said, though it noted the death toll remains imprecise.
"A mismatch between the large number of bodies and limited burial capacity meant that burial took three days," the report said.
Abiy announced military operations in Tigray on November 4, saying they were in response to attacks on federal military camps orchestrated by the TPLF leadership.
His office has seized on media reports blaming pro-TPLF forces for the Mai-Kadra massacre, saying such "atrocities" demonstrate why its leaders must be stripped of all power.
Yet Tigrayan refugees from Mai-Kadra who have fled across the border to Sudan blame government forces for killings there.
The United Nations and human rights groups have called for an impartial probe to determine exactly what happened.
Tigray remains under a communications blackout and media access to the region has been restricted.
The western area of Tigray, where Mai-Kadra is located, saw heavy fighting in the first days of the conflict but is now under federal control.
The fighting has driven more than 40,000 people into Sudan and reportedly killed hundreds.