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

"It targeted at the facilities that TPLF have turned into arms construction and repair armaments sites," government spokesman Legesse Tulu told AFP by text message.

Dr Hayelom Kebede, research director at Mekele's Ayder Referral Hospital, said eight people had been wounded, including a pregnant woman.

"It was heavy and the jet was so close," one local resident told AFP, with witnesses reporting thick clouds of smoke rising up over the city.

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.

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

William Davison, the International Crisis Group's senior analyst for Ethiopia, said the strikes "appear to be part of efforts to weaken Tigray's armed resistance," with the TPLF making gains in areas of the Amhara region to the south of Tigray.

"Along with superior manpower, control of the skies is one of the few remaining areas of military advantage for the federal government."

- 'Surgical operations' -

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.

Much of northern Ethiopia is under a communications blackout and access for journalists is restricted, making claims difficult to independently verify.

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

Legesse, the government spokesman, said the targeted 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, there were two aerial assaults on Mekele, the city held by the TPLF since it was recaptured from government forces in June.

Legesse had initially denied those raids but state media later confirmed the air force had hit TPLF media and communications infrastructure.

The United Nations said Monday's attacks had killed three children and wounded nine people, and voiced alarm about the intensifying conflict in Africa's second most populous country.

- 'Strengthening Tigrayan resolve' -

"The bombing of urban areas... reinforces the impression that Addis Ababa is willing to risk civilian lives in Tigray as part of its military efforts, something also demonstrated by the continued federal constraints on aid flows and refusal to provide electricity, banking, and telecommunications services to the region," the ICG's Davison said.

"As such, the air raids may have the effect of strengthening the Tigrayan resolve to resist, rather than weaken it."

Fighting 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 says up to seven million people in the three regions are now in need of food assistance and other emergency support.

The conflict has seen relations between Ethiopia and the West deteriorate, with its crucial ally Washington calling for sanctions if the warring parties do not commit to a negotiated settlement.