The U.S. is calling for an investigation into an alleged massacre of civilians in Ethiopia's Amhara region, where a local rights group says more than 80 people were killed last week following clashes between soldiers and armed groups.

The U.S. ambassador to Ethiopia, Ervin Massinga, said Friday that the "U.S. government is deeply concerned" by the reports from the town of Merawi and called for "unfettered access by independent human rights monitors as well as an impartial investigation to ensure the perpetrators are brought to justice."

Massinga said in a statement that the reported killings of civilians in Merawi followed "disturbing reports of other violations" in Amhara and elsewhere in Ethiopia, which is gripped by several internal conflicts.

A rebellion broke out in Amhara last April when the government moved to dissolve regional forces and absorb them into the federal army. A militia group known as the Fano launched a surprise assault in August in which they captured towns across Amhara over several days before retreating to the countryside.

Rights monitors have documented a range of human rights abuses by government forces during the conflict, including alleged extra-judicial killings.

On Tuesday, the Ethiopia Human Rights Council said it had received information "showing that massive human rights violations were committed" during fighting in Merawi on Jan. 29. It said more than 80 civilians were killed, mostly men.

The rights group said the killings "were conducted by moving from house to house" during searches. However, it stopped short of laying blame for the shootings, saying it was unable to visit the site, and called for a further investigation.

Until recently, the Fano were allied with the federal military in the war against the Tigray People's Liberation Front in the neighbouring region of Tigray, but the relationship was always uneasy. The two sides began fighting even before the Tigray conflict ended in November 2022 with a peace deal.

Last week, Ethiopia's parliament voted to extend a state of emergency in the Amhara region in an attempt to quash the Fano rebellion.