The strike in Finote Selam on Sunday was the most severe since clashes between members of the Ethiopian army and a local militia known as Fano erupted in towns and cities across Amhara after months of tensions.

The hospital official said he heard the blast while he was on duty at around 0700 GMT.

A market was taking place in the town, he added, and the all the victims who arrived in hospital were "wearing either casual civilian clothing or Sunday traditional clothes".

"The casualties range from a 13-year-old child to the elderly," he said. "I didn't get the chance to see what caused the explosion... but residents said it was a drone strike".

"Twenty-two bodies were brought to the hospital, while four others who were critically injured died soon after arriving".

"We've so far received 55 injured patients out of which more than 40 are gravely injured," he said, speaking anonymously over safety concerns.

A resident who arrived shortly after the strike told AFP he had "helped in the burial of bodies of 30 victims".

He said he saw "a medium sized freight vehicle had been completely destroyed in an air strike with dead bodies strewn around the vehicle".

"I heard the loud sound of an aircraft before the attack," which took place in the centre of the town near a hotel, he said.

Both sources said that at the time of the strike, the town was under the control of Fano, while the resident said the Ethiopian army had arrived on Monday.

- Civilian deaths -

Prime Minister Abiy Ahmed's government imposed a six-month state of emergency across Amhara on August 4 and several cities remain under curfew, although violence eased towards the end of last week.

The unrest revived fears about the stability of Africa's second most populous country, seven months after a peace deal ended a brutal two-year conflict in the neighbouring region of Tigray.

Ethiopia's rights watchdog on Monday voiced "grave concern" over the fierce fighting in Amhara this month, and condemned a wave of arrests of ethnic Amharas.

The Ethiopian Human Rights Commission, an independent state-affiliated organisation, said the fighting in Amhara involved the use of heavy artillery "resulting in the deaths and injuries of civilians".

No casualty figures have been issued by the authorities but doctors in two of the affected cities told AFP last week there had been scores of deaths and injuries among civilians.

The EHRC said it had received credible reports of strikes killing many civilians in three towns, including Finote Selam.

After several days of deadly clashes, the army has reoccupied the main towns in Amhara.

The EHRC said that while heavy fighting had subsided in major urban areas since August 9, "it continues in other parts of the region and remains a major concern until a sustainable solution is in place".