United Nations human rights chief Michelle Bachelet has agreed to an Ethiopian request for a joint investigation in the country's northern Tigray region, where Bachelet says possible war crimes may have been committed.

Fighting between government troops and the region's former ruling party, the Tigray People's Liberation Front (TPLF), has killed thousands of people and forced hundreds of thousands from their homes in the mountainous region of about 5 million.

The United Nations has raised concerns about atrocities being committed in Tigray, while U.S. Secretary of State Antony Blinken has described acts carried out in the region as ethnic cleansing. Ethiopia has rejected Blinken's allegation.

Bachelet "responded positively" to a request from the state-run Ethiopian Human Rights Commission (EHRC) for joint investigations in Tigray, the Office of the High Commissioner for Human Rights spokesman Jonathan Fowler said on Wednesday.

"The U.N. Human Rights Office and the EHRC are now developing an investigation plan, which includes resources needed and practical modalities, in order to launch the missions as soon as possible," Fowler said.

Ethiopia's foreign ministry said on Saturday it was ready to work with international human rights experts to conduct investigations on allegations of abuses.

Amnesty International last month accused Eritrean forces of killing hundreds of civilians over 24 hours in Axum city last year. Eritrea denied that, but the EHRC also described such killings in a rare acknowledgment from the Ethiopian side that Eritrean troops have participated in the conflict.

The United Nations and the United States have demanded that Eritrean troops leave Tigray.

Both the Ethiopian and Eritrean governments have denied Eritrean troops are in Tigray, despite dozens of eyewitness accounts and admissions that Eritreans are there from Tigray's federally-appointed regional administration.