A 2021 coup sparked a multi-sided civil war between Myanmar's military, pro-democracy guerillas and ethnic rebel groups that have long been active in the country's fringes.

Four years of conflict have spurred mass displacement and poverty, and much of the fighting has focused on trade routes where combatants run tollgates to bolster their war chests.

The junta and numerous opposition groups declared a ceasefire to ease relief efforts after a 7.7-magnitude quake hit central Myanmar on March 28, killing more than 3,700 people.

However, three eastern Myanmar residents told AFP fighting has been raging for days around the junta-held towns of Kyondoe and Kawkareik, which sit on a highway leading to the western Thailand border town of Mae Sot.

A resident from an outlying village, who asked to remain anonymous, said the towns had been under attack by "combined forces" from different rebel groups since before Sunday.

"There were air strikes and artillery shots around our village since two days ago," they added. "We have no place to hide."

A resident living a short distance from Kyondoe said their village had been occupied by members of the anti-coup People's Defence Force.

"We are hearing the sounds of air strikes and artillery shooting. We cannot flee to other places now," they said. "We are really scared."

A third resident from Kyondoe, 50 kilometres (30 miles) from the Thai border, said they fled two days ago alongside many neighbours from surrounding villages "to avoid heavy fighting".

The junta said after the earthquake that it would honour a truce until April 22, but would still retaliate against attacks.

As many as 60,000 people are living in tent encampments after the quake, according to United Nations figures.

Junta spokesman Zaw Min Tun accused several rebel groups on Wednesday evening of breaching the truce in recent days, including near Kyondoe and inside Kawkareik.

AFP could not reach Zaw Min Tun for further comment on Thursday.

Monitors agree that the post-quake truce has not held but junta chief Min Aung Hlaing is reportedly due to make a rare trip abroad on Thursday to meet Malaysian Prime Minister Anwar Ibrahim and discuss an extension.

Malaysia is this year's chair of the 10-country Association of Southeast Asian Nations bloc. ASEAN has in the past barred junta officials from its summits over lack of progress on a peace plan.

However, Anwar said he would meet Min Aung Hlaing in Bangkok to discuss prolonging the ceasefire beyond Tuesday to protect Malaysian teams working on quake relief efforts.