At least 11 schoolchildren died in an air strike on a Myanmar village, according to the United Nations children's agency, an attack the country's junta said targeted rebels hiding in the area.

U.N. Secretary-General Antonio Guterres on Tuesday condemned the strike, according to his office, which said at least 13 people died, including the 11 students.

The Southeast Asian country has been in chaos since the military seized power in a coup February 1, 2021, with nearly 2,300 civilians killed in a crackdown on dissent according to a local monitoring group.

The Sagaing region in the country's northwest has experienced some of the fiercest fighting, and clashes between anti-coup fighters and the military have seen entire villages burned down.

The U.N. children's agency UNICEF condemned Friday's violence in Depeyin township in Sagaing.

'At least 15 children from the same school are still missing,' UNICEF said in a statement issued Monday, calling for their immediate safe release.

Guterres, who on Tuesday was hosting world leaders at the U.N. General Assembly, 'strongly condemns the attacks by Myanmar armed forces on a school in Let Yet Kone' and offered his condolences to victims' families, his spokesman Stephane Dujarric said in a statement.

Such attacks on schools in contravention of international humanitarian law constitute 'grave violations against children in times of armed conflict strongly condemned by the Security Council,' the Guterres spokesman said, calling for the perpetrators to be held accountable.

The junta said they had sent troops in helicopters to Let Yet Kone after receiving a tip that fighters from the Kachin Independence Army (KIA), an ethnic rebel group, and from a local anti-coup militia were moving weapons in the area.

The military accused the rebel fighters of using civilians as human shields and said it had seized mines and explosives from the village.

'Security members gave necessary medical treatment and arranged to send patients to a nearby hospital,' the military said in a statement.

Junta spokesman Zaw Min Tun on Tuesday accused the KIA of taking villagers to a monastery and then firing on troops from there.

A villager contacted by AFP rejected the military's suggestions there were fighters in the area.

'They just attacked the school. They say someone attacked them, then they fought back but this is not true,' said the villager, who spoke on condition of anonymity for their own safety.

The villager said the military had taken away some of the bodies and detained multiple people, including children and teachers.

ASEAN has led so far fruitless diplomatic efforts to resolve the crisis in Myanmar. The group's leaders meet in Phnom Penh in November.