The latest strike was aimed at a facility "currently serving TPLF for military training", government spokesman Legesse Tulu told AFP, referring to the Tigray People's Liberation Front rebel group.

However it was unclear if the strike was successful, with TPLF spokesman Getachew Reda telling AFP the group's air defence units managed "to foil its mission".

"I can see it's trying a third time and we will see what will happen," he said.

But federal official Selamawit Kassa, state minister of government communication services, disputed Getachew's claim, telling AFP "it was a successful mission".

Prime Minister Abiy Ahmed's government has been locked in a nearly year-long war against the TPLF, though Tigray itself has seen little combat since late June, when the rebels seized control of much of Ethiopia's northernmost region and the military largely withdrew.

On Monday Ethiopia's air force launched two strikes in Tigray's capital Mekele that the UN said killed three children and wounded several other people.

And on Wednesday it bombed TPLF weapons caches in Mekele and in the town of Agbe, which lies about 80 kilometres (50 miles) to the west.

A hospital official told AFP that Wednesday's strike in Mekele injured at least eight people, including a pregnant woman.

TPLF spokesman Kindeya Gebrehiwot told AFP there were no casualties from Thursday's strike.

On Twitter, though, he said the bombardment hit an area "where civilians reside", describing it as "a further attempt to terrorize our people for the loss on the battlefield".

The international community has voiced alarm about the latest attacks.

A US State Department spokesman said Wednesday that Washington "condemns the continuing escalation of violence, putting civilians in harm's way."

- Rebels press south -

The air strikes come amid reports of heavy fighting in the Amhara region south of Tigray, where the TPLF launched an offensive in July.

On Wednesday Getachew claimed on Twitter that TPLF fighters had taken control of at least two new towns in the region, putting the cities of Kombolcha and nearby Dessie -- where tens of thousands have sought refuge from the rebel advance -- "within artillery range".

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

Dessie residents on Thursday reported a heavy military presence in the area as displaced civilians from conflict-hit towns farther north continued to arrive.

"People are coming to Dessie from Hayk [town] while others are leaving in fear of military conflict," said one resident, speaking on condition of anonymity to protect relatives trapped in TPLF-controlled areas.

"Some businesses are shut down. The city is relatively calm today in comparison to what has been observed in the past three days."

Government officials have issued multiple calls in recent months for mass mobilisation to fight the TPLF, and diplomats estimate tens of thousands of people have enlisted.

Amhara regional president Yilkal Kefale called Thursday for armed Amharas to converge on Dessie to defend it.

"It is high time that the Ethiopian people must stand in unison in order to eliminate its common enemy," he said.