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

The military has set polls starting December 28 -- touting the vote as an off-ramp to fighting -- but rebels have pledged to block it from the territory they control, which the junta is battling to claw back.

A military jet bombed the general hospital of Mrauk-U in western Rakhine state, bordering Bangladesh, on Wednesday evening, said on-site aid worker Wai Hun Aung.

"The situation is very terrible," he said. "As for now, we can confirm there are 31 deaths and we think there will be more deaths. Also there are 68 wounded and will be more and more."

At least 20 shrouded bodies were visible on the ground outside the hospital overnight.

A junta spokesman could not be immediately reached for comment.