Dozens of people have been stabbed and hacked to death in Ethiopia’s Tigray region, according to Amnesty International.
The claims come as federal troops claimed major advances in their offensive against local forces.
“This is a horrific tragedy,” Amnesty said in a statement, citing witnesses as blaming local rulers, the Tigray People’s Liberation Front (TPLF), for the killings, which it said took place two days ago.
Earlier, Ethiopian prime minister Abiy Ahmed had accused his opponents of committing atrocities during a week of fighting that threatened to destabilise the Horn of Africa.
Mr Abiy said Ethiopia‘s military had defeated local forces in the west of the state.
Airstrikes and ground combat have killed hundreds, sent refugees flooding into Sudan, stirred the country’s ethnic divisions and raised questions over the credentials of the leader – Africa’s youngest at just 44.
With communications down and media barred, independent verification of the status of the conflict has been impossible.
Amnesty said the killings had taken place in the town of Mai Kadra in Tigray’s southwest, and that witnesses described bodies with wounds that appeared to have been inflicted with knives or machetes.
“Amnesty International has not yet been able to confirm who was responsible for the killings, but has spoken to witnesses who said forces loyal to the TPLF were responsible for the mass killings, apparently after they suffered defeat from the federal EDF forces,” it said.
There was no immediate response from the Ethiopian government or Tigray’s local leaders.
Mr Abiy has accused the TPLF of starting the conflict by attacking a federal military base and defying his authority, while the Tigrayans say they have been persecuted during his two-year rule.
More than 11,000 Ethiopian refugees have crossed into Sudan since fighting started and aid agencies say the situation in Tigray is becoming dire.
Even before the conflict, 600,000 people there were reliant on food aid.