Washington DC - President Donald Trump on Friday vowed the US would assist Myanmar after it was hit by a huge earthquake, following a rare plea for aid by the Southeast Asian nation's ruling junta.

"It’s terrible," Trump told reporters in the Oval Office about the quake when asked if he would respond to the appeal by Myanmar's military rulers.

"It's a real bad one, and we will be helping. We've already spoken with the country."

The huge 7.7-magnitude earthquake hit Myanmar and Thailand on Friday, killing more than 150 people and injuring hundreds.

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Myanmar junta chief Min Aung Hlaing had earlier invited "any country, any organization" to help with relief, in a speech aired on state media.

Four years of civil war sparked by the military seizing power have ravaged Myanmar's infrastructure and health care system, leaving it ill-equipped to respond to such a disaster.

The US has in recent years been pressing Myanmar's rulers for progress on key concerns such as freeing political prisoners and reducing violence.

Myanmar's junta has meanwhile been fostering ties with key ally Russia, with leader Min Aung Hlaing visiting President Vladimir Putin in Moscow earlier this month.

The two countries are talking about a plan for Moscow to help build a small nuclear power plant in Myanmar.