The raids mark a sharp escalation in the near year-long conflict in northern Ethiopia pitting government forces and their allies against the TPLF, Tigray's once dominant ruling party.

The government said the latest strike on Mekele was aimed at weapons caches.

"It targeted at the facilities that TPLF have turned into arms construction and repair armaments sites," Legesse Tulu, head of the Government Communication Service, told AFP by text message.

It was not immediately known if there were any casualties from the strike, which the TPLF said hit a residential area.

"It was heavy and the jet was so close," one local resident told AFP, adding that it had destroyed an industrial site.

"It has burned the whole compound. We don't know the casualties but now the whole company is burned to ash."

Prime Minister Abiy Ahmed's government, barely two weeks into its new term, appears to be pressing a new offensive against the TPLF, which dominated national politics for almost three decades before he took power in 2018.

The conflict has already killed untold numbers of people and triggered a deep humanitarian crisis, with the United Nations saying up to two million people have been displaced and hundreds of thousands plunged into famine-like conditions.

Tigray, a region of five million people, remains under a de facto blockade, with the warring parties each accusing the other of hindering the delivery of desperately needed aid.

- 'Alarming intensification' -

TPLF spokesman Getachew Reda said Wednesday's bombing raid had targeted a residential area of Mekele "causing injury to civilians and harm to property".

"Abiy's reaction to his losses in the ongoing fighting is to target civilians hundreds of kms away from the battlefield," he said on Twitter.

Legesse, the government spokesman, said the site had been "appropriated by the TPLF as a heavy weapons storage, manufacturing and repair site" and accused the TPLF of using ordinary people as human shields.

"We confirm and assure these surgical operations have not any intended harm to civilians," he said.

On Monday, Ethiopia's air force carried out two aerial assaults on Mekele, the city held by the TPLF since it was recaptured from government forces in June.

The United Nations said those raids -- the first since the early stages of the conflict -- had killed three children and wounded nine people.

"The intensification of the conflict is alarming," said Jens Laerke, spokesman for the UN Office for the Coordination of Humanitarian Affairs (OCHA).

UN chief Antonio Guterres and the US State Department on Monday had both voiced deep concern about the escalating violence and urged an immediate end to hostilities.

The Ethiopian government spokesman had initially denied reports about Monday's air strikes as an "absolute lie" but state media later confirmed the military had hit TPLF media and communications infrastructure.

The conflict in Africa's second most populous country first erupted last November after Abiy -- the 2019 Nobel Peace Prize winner -- sent troops to Tigray to topple the TPLF.

He said the move came in response to TPLF attacks on federal army camps and promised a swift victory.

But in a dramatic turnaround, by late June the TPLF had regrouped and retaken most of the region including Mekele.

Since then, the rebels have pushed south from Tigray into the neighbouring regions of Amhara and Afar.

The UN said Wednesday that up to seven million people in the three regions were now in need of food assistance and other emergency support.