The Southeast Asian nation has been in turmoil since the military ousted Aung San Suu Kyi's government last year, sparking widespread armed resistance.

The junta has responded with a crackdown that rights groups say includes razing villages, mass extrajudicial killings and airstrikes on civilians.

Since the coup and as of last month, 1,017,000 people have been internally displaced, UNICEF said in a statement on Thursday.

It added that more than half of those forced to flee are in the country's northwest Sagaing region, which has seen some of the fiercest fighting.

There were "significant challenges" to delivering humanitarian assistance in the region, UNICEF said.

Sagaing is crisscrossed by junta troops, pro-military militias and anti-coup fighters and where authorities regularly cut internet access.

More than 12,000 civilian properties were thought to have been burned or destroyed across Myanmar since the coup, the UN humanitarian agency UNOCHA said in May.

Last month, at least 11 schoolchildren died in an airstrike and firing on a village in Sagaing, an attack the junta said targeted rebels hiding in the area.

Diplomatic efforts to end the crisis are moribund.

A "consensus" brokered last year by the Association of Southeast Asian Nations (ASEAN) aimed at facilitating dialogue between the military and its opponents and the delivery of humanitarian aid has been largely ignored by the junta.