A military jet bombed late Wednesday the general hospital of Mrauk-U in western Rakhine state, bordering Bangladesh, two aid workers said.

"Those killed or injured were not civilians, but terrorists and their supporters," said an article in the state-run Global New Light of Myanmar (GNLM).

The ruling junta has increased air strikes year-on-year since the start of the country's civil war, conflict monitors say, after seizing power in a 2021 coup ending a decade-long experiment with democracy.

The United Nations on Thursday demanded an investigation, saying the attack could constitute a war crime.

Health workers and patients were killed, and "hospital infrastructure was severely damaged, with operating rooms and the main inpatient ward completely destroyed," said World Health Organization chief Tedros Adhanom Ghebreyesus on X.

Rakhine state is controlled almost in its entirety by the Arakan Army (AA), an ethnic minority separatist force active long before the military toppled the civilian government of democratic leader Aung San Suu Kyi.

The separatist force said in a statement that 33 people were killed and 76 wounded in the strike.

People's Defence Forces (PDF) have also risen up to oppose the military coup four years ago.

The junta "carried out necessary security measures and launched a Counter-Terrorism Operation on 10 December against the buildings being used as a base by AA and PDF terrorists," GNLM said.