A suspected air strike at the weekend in Ethiopia's Amhara region killed at least 26 people, a hospital official said on Monday, as a state-appointed rights group detailed widespread killings of civilians since fighting broke out this month.

Federal forces managed late last week to push Fano militiamen out of most major towns in Amhara, but clashes continue in other parts of the region, the Ethiopian Human Rights Commission (EHRC) said in a statement.

The fighting, which has been fuelled by Fano accusations that the federal government is trying to weaken Amhara's defences, is Ethiopia's biggest security crisis since a two-year civil war in the northern Tigray region ended last November.

Ethiopia's government denies the allegations by Fano, an informal militia that backed federal forces during the Tigray war. Spokespeople for the government, the military and Prime Minister Abiy Ahmed did not respond to requests for comment on Monday about the suspected air strike or EHRC's statement.

The suspected strike hit the town centre of Finote Selam on Sunday, said the hospital official, who asked not to be named for security reasons.

The hospital official said four people died at the hospital and another 22 either at the scene or on their way to hospital. Fifty-five more are being treated for injuries sustained in the explosion, the official said.

Tikikil Kumlachew, a university teacher who was visiting a relative in the hospital from an unrelated incident, said he had seen 14 bodies there and been told by a medical worker that another 12 had died.

"The explosion shook the city. I don't know if it was a drone or something else. But it fell from the sky," said

In its statement on Monday, the EHRC said it had received credible reports that strikes and shelling in Finote Selam and other towns had resulted in civilian casualties, without specifying when these events occurred.

EHRC's statement said its investigators had documented a variety of incidents since the conflict started, including the killing of protesters who blocked roads, the looting of weapons and ammunition from police stations and prisons, and the targeting of Amhara regional administration officials.

In Amhara's capital Bahir Dar, civilians were killed on the streets or outside their houses, EHRC said, adding there were credible reports of "many civilian casualties" in Gondar, the region's second biggest city, and extra-judicial killings by security forces in Shewa Robit.

In Addis Ababa, the capital, there have also been widespread arrests of civilians of ethnic Amhara origin, it said.

(Reporting by Hereward Holland; Editing by Aaron Ross and Andrew Cawthorne)