The raid came only hours after the Ethiopian government had issued a call for "national reconciliation", and sparked renewed calls from an alarmed international community for an end to the brutal conflict.

The UN Office for the Coordination of Humanitarian Affairs (OCHA) said in a statement to AFP that the attack at midnight Friday in the town of Dedebit in northwestern Tigray had "caused scores of civilian casualties including deaths", according to its preliminary information.

"Humanitarian partners suspended activities in the area due to the ongoing threats of drone strikes," it said.

Tigray rebels said Saturday that the attack had killed 56 people, while an official at the region's main hospital reported 55 dead and 126 injured.

It was not possible to independently verify the claims because access to the war-ravaged region is restricted and it remains under a communications blackout.

There was no response to requests for comment from Ethiopian government officials.

OCHA said the lack of essential supplies, especially medical supplies and fuel, was "severely disrupting the response to the injured, and (has) led to the nearly total collapse of the health system in Tigray".

"The intensification of air strikes is alarming, and we once again remind all parties to the conflict to respect their obligations under international humanitarian law," it said.

The fighting between forces loyal to Prime Minister Abiy Ahmed and the rebel Tigray People's Liberation Front (TPLF) has killed thousands of people and created a deep humanitarian crisis in the north.

Tigray itself is under what the UN calls a de facto blockade that is preventing life-saving food and medicine from reaching its six million people, including hundreds of thousands in famine-like conditions.

- 'Unacceptable' -

The Dedebit strike came the same day that the Ethiopian government announced an amnesty for several senior officials from the rebel Tigray People's Liberation Front (TPLF) and other high-profile opposition leaders in what it said was a bid to foster national dialogue and "unity".

The amnesty has been welcomed by the international community as a possible way out of the fighting that has threatened to tear apart Africa's second most populous country.

It followed a dramatic turnaround in fortunes on the battlefield, with the rebels retreating to their Tigray stronghold at the end of December in the face of a military offensive that saw government forces retake a string of strategic towns.

Although there appeared to be a lull in fighting since, the rebels have accused the government of continuing to conduct deadly drone attacks on Tigray.

OCHA reported last month that dozens of civilians were reportedly killed in the last days of December in a barrage of air raids in Tigray.

And the United Nations reported this week that three Eritrean refugees including two children had been killed in an air strike Wednesday on a refugee camp in Tigray.

The US Bureau of African Affairs has described the attacks as "unacceptable".

"We redouble our call for an immediate end to hostilities, the prompt launch of an inclusive national dialogue, and unhindered access so aid can reach all Ethiopian communities in need," it said on Twitter.