A federal police officer stands guard as people gather during a protest against purported fake news and foreign meddling at the British Embassy of Ethiopia in Addis Ababa, Ethiopia, on November 25, 2021. AFP
The assault on Gambella on Tuesday triggered an hours-long gunfight between security forces and the Oromo Liberation Army (OLA), a rebel group which is branded a terrorist organisation by the Ethiopian government.
After soldiers successfully repelled the attack by the OLA and a local armed group, "residents faced various human rights abuses at the hands of the Gambella regional... forces," the EHRC, a state-affiliated independent rights body, said in a statement.
"EHRC has, from witness accounts and video evidence it has received, understood that individuals suspected of participating in the (rebel) attack or collaborating in the attack were killed," it said, adding the security forces carried out "door to door executions".
The rights body urged the authorities to "conduct an investigation and ensure accountability into illegal acts committed by security forces".
The statement was released the same day that a video circulating on social media, whose authenticity could not be immediately confirmed, showed a man, allegedly of Oromo ethnicity, being shot dead by several uniformed men.
A spokesman for the Gambella regional authorities said in a press release that the "information being circulated on some social media platforms suggesting that an ethnic-based assault has occurred is false".
He added that the government was taking action against some members of the security forces for unethical behaviour following an investigation.
Odaa Tarbii, spokesman for the OLA, which is active in the neighbouring Oromia region, said 11 civilians had been killed in Gambella since Tuesday's attack.
"Security forces in Gambella have gone on a killing spree targeting anyone they suspect of being #Oromo," he said on Twitter.
The Gambella region borders South Sudan and has in the past suffered incursions by armed fighters from the neighbouring 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.
Ethiopia's government declared a "humanitarian truce" in March, allowing limited supplies of international aid to the stricken Tigray region for the first time since mid-December.