Colonel Getnet Adane said Tuesday's operation in the town of Togoga "dismantled" armed forces loyal to Tigray's ousted ruling party and cautioned that the rebels were known to wear civilian clothes.

"We do not accept that this operation targeted civilians," the spokesman said.

But survivors and health workers described aerial explosions striking a busy market at the peak of trading, killing and injuring dozens, including children.

The United Nations has called for an urgent investigation into the strike.

Ambulances left Mekele on Thursday to try to reach the scene some 30 kilometres (18 miles) from the regional capital after earlier being denied access by the army.

Families huddled anxiously outside the hospital for news of their loved ones.

- Official denial -

Victims at the hospital bore shrapnel wounds, burns and disfigured limbs, and doctors were forced to perform amputations to save lives.

"Looking at the injuries, it does suggest it was a bombing," said the doctor of a 12-year-old girl whose right arm was mangled in the blast.

Survivors spoke of huge devastation as bombs tore through the market around 1:00 pm, reducing nearby homes to rubble and burying people under the ruins.

Some estimated more than 50 people died in the attack. AFP could not independently verify these accounts.

But the military spokesman said rebel fighters dressed in civilian clothes had gathered in Togoga to celebrate "Martyr Day" when they were attacked.

"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.

He 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 operation was conducted on June 22 against the remnants of the TPLF," Getnet said.

"An operation carried out by the Ethiopian National Defence Force has dismantled that force."

The attack came as vote counting was under way following Monday's national elections in Ethiopia. However, the conflict in Tigray meant no vote was held there.

- Global outrage -

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

The European Union said if ambulances were indeed prevented from reaching the scene it would represent a grave violation of international law.

Ethiopia's foreign ministry spokesman Dina Mufti rejected the criticism, saying the rebels used human shields and places of worship 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 also 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".

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.

In recent days, as votes were cast and counted across much of the vast nation of 110 million people, there were reports of rebel advances in Tigray.

They included the brief occupation of the key town of Adigrat in the far north, and Wukro, further south nearer Mekele, residents told AFP.