The UN Human Rights Commissioner is warning that reports of mass killings in Ethiopia, would, if verified, amount to war crimes.
This comes after Amnesty International reported that scores of civilians had been killed in a town in Tigray state.
Speaking in Geneva, Michelle Bachelet called for a full investigation and said those responsible must be held accountable.
The authorities in Tigray have denied eyewitness reports that Tigrayan forces carried out the killings.
Ms Bachelet said the first priority must be ending the fighting.
The UN fears the conflict could spiral out of control and even spread across Ethiopia’s borders.
Thousands of people are already fleeing the fighting into neighbouring Sudan.
The UN refugee agency said many are children who are arriving exhausted and terrified.