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 fighting and air strikes 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."
"If confirmed as having been deliberately carried out by a party to the current fighting, these killings of civilians would of course amount to war crimes," she said in a statement.
Amnesty said it had not been able to confirm who was responsible for the killings, however witnesses blamed forces backing the region's ruling party, the Tigray People's Liberation Front (TPLF).
Witnesses also reported the identity cards of some victims indicated they were from the Amhara region, an area with a long history of tensions with Tigrayans, notably over land.
Thousands of Amhara militiamen have deployed to the Tigray border to fight alongside federal forces.
Tigrayan leader Debretsion Gebremichael told AFP on Friday the accusations were "baseless".
Abiy says his military operation came in response to attacks on two federal military camps by the TPLF, which once dominated Ethiopian politics and claims it has been sidelined and targeted under Abiy.
The party denies carrying out the attacks.
Long-running tensions between Abiy and the TPLF hit a new low in September when Tigray pressed ahead with its own elections, insisting Abiy was an illegitimate leader after national polls were postponed due to the coronavirus.
On Friday Abiy addressed the region, especially its soldiers, urging them to "rise up" and side with the national army.
"This mischievous force is surrounded on all sides. It is a force in its final throes of death. Your children are suffering death and injuries on the frontline," he said in the Tigrinya language in a speech broadcast on Facebook.
"Rise up against the clique or defect to the Ethiopian Defense Forces, use the opportunity given to you by your country in the next two or three days... save yourself."
A communications blackout in Tigray has made it difficult to verify competing claims on the ground, but Abiy has vowed to deliver a decisive win "in a relatively short period of time".
"This is a daydream, just a daydream," Debretsion said. "We are proud people who can defend ourselves. This is a burial ground for invaders."
Bachelet warned that if the conflict continues "there is a risk this situation will spiral totally out of control, leading to heavy casualties and destruction, as well as mass displacement within Ethiopia itself and across borders."
"I am also extremely alarmed at reports of cuts to essential water and electricity supplies, in addition to the communications blackout and blocking of access by road and air."
There are mounting worries about how Tigray's population is faring after intensified fighting and several rounds of air strikes that Abiy's government says targeted fuel and weapons depots.
Thousands have already crossed the border into neighbouring Sudan, while Debretsion said hundreds of thousands had been displaced within Tigray.
He also said civilians had been killed in government air strikes in the regional capital Mekele, and in the city of Adigrat close to the border with Eritrea.
"People are running in every corner. So the most important consequence of the conflict currently is displacement. Of course there are casualties, but we don't have the numbers. This is too big to manage," Debretsion said.
Ethiopian state media reported that an arrest warrant had been issued for Debretsion and other TPLF leaders.
On Friday, an African Union official confirmed the body had replaced its head of security, an ethnic Tigrayan, after Ethiopia's defence ministry complained he was "assumed to be not honest" and could jeopardise the relationship between Ethiopia and the AU, which is headquartered in the capital Addis Ababa.
AU chief Moussa Faki Mahamat complied with the request, and a letter from his office dated Wednesday ordered the official, Gebre-egzhiaber Mebratu Melese, be terminated "with immediate effect."