Details of the bloody attack on Togoga town, 30 kilometres (18 miles) northwest of the regional capital Mekele, on Tuesday were slow to emerge partly because soldiers initially blocked emergency workers from accessing the area.

By Thursday, hospitals in Mekele were treating at least 73 people, including young children.

Victims at the hospital suffered shrapnel wounds and burns, and in some cases doctors were forced to perform amputations to save lives.

- Rebels dressed as civilians -

The Ethiopian military admitted carrying out the attack but said it targeted rebel fighters, not civilians.

The health officer told AFP at least 64 people had died.

"The air strike was in the market area, so many, many people were injured," said Mulu Atsbaha, an advisor to the Tigray regional administration on maternal and child health.

He said the toll had been collated from residents of Togoga and "confirmed with local leaders".

Survivors spoke of huge devastation as aerial explosions tore through the busy market around 1 pm, killing and injuring dozens, reducing nearby homes to rubble and burying people under the ruins.

But Ethiopia's military spokesman said rebel fighters dressed in civilian clothes, gathered in Togoga to celebrate "Martyr Day", were attacked.

"We do not accept that this operation targeted civilians," Colonel Getnet Adane told AFP.

"It is a clear fact that both the remnants of the TPLF and its militia dress in civilian clothes," he said, referring to the renegade former regional leadership.

Genet also denied the army targeted a market, adding that while it was market day on Tuesday, "in Ethiopia, people go to the markets in the morning, and by the afternoon they are usually deserted."

The attack came as vote counting was under way following Monday's national elections in Ethiopia.

No vote was held in Tigray because of the conflict, and the region has seen an upsurge in fighting and rebel advances in recent days.

They included the brief occupation of the key town of Adigrat in the far north, and Wukro, further south nearer Mekele, residents told AFP, while heavy shelling was reported to the north of the regional capital on Thursday morning.

Flights in and out of Mekele were disrupted for a second day Thursday.

Prime Minister Abiy Ahmed sent troops to Tigray in November to oust the dissident regional leadership, promising a swift victory.

But nearly eight months later, fighting continues, which has triggered a humanitarian crisis with the UN warning 350,000 people are on the brink of famine.

- International outrage -

The strike has provoked international outrage, with the United States calling it a "reprehensible act".

The European Union said the blocking of ambulances from reaching the scene would be a grave violation of international law, while the United Nations called for an urgent investigation into the strike.

Ethiopia's foreign ministry spokesman Dina Mufti rejected the criticism, accusing the rebels of using human shields to draw attacks.

"The Ethiopian government does not target civilians. It is only moving to pick up people wanted by the law," he told reporters on Thursday.

Dina complained that international attention was focused on Tuesday's deadly attack, rather than Monday's polls, saying foreign powers "didn't care to give statements on this historical election".