Ethiopia on Friday launched fresh air strikes on the capital of the Tigray region, the fourth day this week the city has come under attack, a government spokeswoman told AFP.
Friday's operation targeted a training centre used by the Tigray People's Liberation Front (TPLF) rebel group, Billene Seyoum said, adding that it was "also serving as a battle network hub by the terrorist organization".
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 the town of Agbe, 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.
A fourth strike in Mekele on Thursday did not result in any casualties, according to medics and the TPLF.
There was no immediate word on casualties Friday, but two humanitarian sources said a UN flight bound for Mekele was forced to return to Addis Ababa because of the strikes.
The international community has voiced alarm about the attacks.
A US State Department spokesman said Wednesday that Washington "condemns the continuing escalation of violence, putting civilians in harm's way".
The air raids come amid reports of heavy fighting in the Amhara region south of Tigray, where the TPLF launched an offensive in July.
On Wednesday, TPLF spokesman Getachew Reda claimed on Twitter that rebel 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 their advance -- "within artillery range".
Much of northern Ethiopia is under a communications blackout and access for journalists is restricted, making battlefield claims difficult to verify independently.
Dessie residents on Thursday reported a heavy military presence in the area as displaced civilians from conflict-hit towns farther north continued to arrive.
Meanwhile the UN has again sounded the alarm about dire humanitarian conditions in Tigray, saying in a report Thursday that some aid groups had been forced to suspend food distribution for lack of fuel.
AFP has documented starvation deaths in multiple parts of the region, citing internal documents from aid groups active there.
The UN said last week the number of young children hospitalised due to severe malnutrition between February and August was double the number recorded during the same period last year.
Some 2.5 per cent of screened children were diagnosed with severe malnutrition during the past week, the UN said Thursday, up from 2.3 percent the week before.
Thursday's report also noted that during the week ending October 13, only 52,000 people in Tigray received food assistance, or one percent of the 5.2 million that aid groups are targeting.
"To reach 5.2 million people with food assistance within a six-week cycle, partners are expected to assist at least 870,000 people on average per week," the report said.