The Ethiopian government has said it was only aiming at 'military targets', but UN and EU officials say there were civilian casualties in 'barbaric attack'.
The UN children's agency Unicef has condemned an airstrike that "hit a kindergarten" in the Ethiopian region of Tigray, with the EU also calling for respect for international law protecting civilians.
Rebel authorities in the Ethiopian province of Tigray claimed that a kindergarten had been bombed Friday by Ethiopia's air force, while the government in Addis Ababa claims it was only aiming at "military targets."
"Unicef strongly condemns the air strike in Mekele, the capital of the Tigray region of Ethiopia. The strike hit a kindergarten, killing several children and injuring several," the organisation's executive director, Catherine Russell, said in a tweet.
"Once again, children have paid a heavy price for escalating violence in northern Ethiopia. For almost two years, children and their families in the region have been suffering from this conflict. It must stop," she added.
There was no immediate reaction from the Ethiopian government to the UN statements.
Without mentioning the target, the European Commissioner for Crisis Management, Janez Lenarcic, condemned the strike, which he said "resulted in the death of civilians,". and called for respect for international humanitarian law.
"Civilians are not a target," he tweeted.
"Reports of air strikes in Tigray resulting in civilian casualties are appalling. All parties must respect international humanitarian law and make the protection of civilians their priority," tweeted UK Africa Minister Vicky Ford.
An official at Ayder Hospital, the main hospital in the town of Mekele, said in a message to AFP on Friday that his facility had received four fatalities, including two children, and nine injuries.
Tigray's official television said "seven civilians including three children" had been killed and broadcast pictures showing what looked like a devastated playground and a building with brightly painted walls damaged.
Journalists have no access to northern Ethiopia, making independent verification impossible. The mobile and internet networks are also unreliable and no officials could be reached in Tigray on Saturday.
The director-general of the World Health Organisation (WHO), Ethiopian Tedros Adhanom Ghebreyesus, himself a native of Tigray, tweeted that he was "at a loss for words" in the face of "this terrible event and the loss of innocent life", describing the strike as "barbaric".
Fighting resumed Wednesday in northern Ethiopia, ending a five-month truce between the federal government and rebel authorities in Tigray, who blame each other for the resumption of hostilities.
Until the strike on Mekele on Friday, fighting was limited to two areas around the south-eastern border of Tigray.
The rebels claimed that an aircraft had "dropped bombs on a residential area and a kindergarten". The Ethiopian government responded that the Ethiopian military aircraft only targeted "military sites" and accused the Tigrayan rebels of staging the scene "to claim that the aircraft attacked civilians".