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 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.

A fourth strike in Mekele on Thursday did not result in any casualties, according to medics and the TPLF, and there was no immediate word on casualties Friday.

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".

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