"The unremitting violence inflicted on civilians, despite a ceasefire nominally declared in the wake of the devastating earthquake on 28 March, underscores the need for the parties to commit to, and implement, a genuine and permanent nationwide halt to hostilities and return to civilian rule," UN rights chief Volker Turk said in a statement.

A multi-sided conflict has engulfed Myanmar since 2021, when Min Aung Hlaing's military wrested power from the civilian government of Aung San Suu Kyi.

Following the 7.7 magnitude quake, the junta joined opponents in calling a temporary halt to hostilities on April 2 for relief to be delivered.

But Turk said that since the quake and up to April 29, "the military has reportedly launched at least 243 attacks, including 171 air strikes, with over 200 civilians reportedly killed".

"The vast majority of attacks," he added, had happened after the ceasefire took effect.

While the military renewed once its "largely unobserved ceasefire", the truce had been allowed to expire on April 30, Turk said.

"It is imperative that the military immediately stop all attacks on civilians and civilian objects," he insisted.

The UN rights chief decried how "the relentless attacks affect a population already heavily beleaguered and exhausted by years of conflict", compounded by the impact of the quake.

Nearly 20 million people in the country already rely on humanitarian assistance, he said, stressing that people in Myanmar "need food, water and shelter".

"They need, and must have, peace and protection," he said.

"International law is clear that humanitarian aid must be able to reach those in need without impediment."

Turk urged the military to "put people first, to prioritise their human rights and humanitarian needs and to achieve peaceful resolution to this crisis".

"Instead of further futile investment in military force, the focus must be on the restoration of democracy and the rule of law in Myanmar."