The United Nations warned Friday of possible war crimes in Ethiopia’s northern region of Tigray, after 10 days of fighting that the country’s prime minister claimed had his enemy “in the final throes of death”.

Prime Minister Abiy Ahmed, winner of last year’s Nobel Peace Prize, ordered military operations in Tigray last week, shocking the international community which fears the start of a long and bloody civil war.

Hundreds are reported to have been killed, some in a gruesome massacre reported by Amnesty International, and thousands have fled the fighting and airstrikes in Tigray, whose leaders Abiy accuses of seeking to destabilise the country.

UN rights chief Michelle Bachelet called for a full investigation into the report of mass killings in the town of Mai-Kadra, where Amnesty said it had “digitally verified gruesome photographs and videos of bodies strewn across the town or being carried away on stretchers.”