Ethiopian Human Rights Commission said Wednesday that security forces had killed dozens of civilians in Gambella in June suspected of collaborating with rebels after an attack on the southwestern city.

The joint assault on June 14 by the Gambella Liberation Front (GLF) and the Oromo Liberation Army (OLA), a rebel group branded a terrorist organization by the Ethiopian government, triggered an hourslong gunfight.

After soldiers successfully repelled the attack, regional forces killed anyone suspected of participating or collaborating in the assault, the EHRC said in a 13-page report based on interviews with 58 people including victims, their families and eyewitnesses.

The state-affiliated independent rights body had earlier accused security forces of carrying out "door-to-door executions" of residents, according to a statement released days after the attack.

On Wednesday, the EHRC said it had "verified that at least 50 civilians have been killed individually and in mass extrajudicial executions primarily by the region's security forces between June 14-16, with (victims) accused of harboring OLA fighters and having firearms."

"The bodies of civilians who were killed by security forces were collected by the region's special forces and regular police ... and buried en masse," the rights body said, with victims' families denied access to the remains.

The victims included mentally ill people, while at least 25 others suffered injuries, with some residents tortured and beaten. The rights body said OLA and GLF fighters killed seven civilians, with six other people dying during the gunfight between the rebels and soldiers.

The EHRC said the region's police commission told the rights body that local officials had collected and buried bodies lying on the streets. The regional police said the civilians were killed by rebels and that no one had claimed the bodies that were buried by the city administration.

The Gambella region borders South Sudan and has in the past suffered incursions by armed fighters from the neighboring country. The OLA last year forged an alliance with the Tigray People's Liberation Front (TPLF), which has been locked in conflict with federal forces in northern Ethiopia since November 2020.