The toll from Myanmar's earthquake continued to rise on Sunday, as foreign rescue teams and aid rushed into the country where hospitals were overwhelmed and some communities scrambled to mount rescue efforts with limited resources.

The 7.7-magnitude quake, one of Myanmar's strongest in a century, struck on Friday, leaving around 1,700 people dead, 3,400 injured and over 300 missing as of Sunday, the military government said.

The junta chief, Senior General Min Aung Hlaing, warned that the number of fatalities could go up and his administration faced a challenging situation, state media reported, three days after he made a rare call for international assistance.

India, China and Thailand are among Myanmar's neighbours that have sent relief materials and teams, along with aid and personnel from Malaysia, Singapore and Russia.

"The destruction has been extensive, and humanitarian needs are growing by the hour," the International Federation of Red Cross and Red Crescent Societies said in a statement.

"With temperatures rising and the monsoon season approaching in just weeks, there is an urgent need to stabilise affected communities before secondary crises emerge."

The United States pledged US$2 million in aid "through Myanmar-based humanitarian assistance organisations" and said in a statement that an emergency response team from USAID, which is undergoing massive cuts under the Trump administration, is deploying to Myanmar.

Critical infrastructure – including bridges, highways, airports and railways – across the country of 55 million lie damaged, slowing humanitarian efforts while the conflict that has battered the economy, displaced over 3.5 million people and debilitated the health system rages on.

In some areas near the epicentre, residents said government assistance was scarce, leaving people to fend for themselves.

"It is necessary to restore the transportation routes as soon as possible," Min Aung Hlaing told officials on Saturday, according to state media. "It is necessary to fix the railways and also reopen the airports so that rescue operations would be more effective."

The US Geological Service's predictive modelling estimated Myanmar's death toll could eventually top 10,000 and losses could exceed the country's annual economic output.

Hospitals in parts of central and northwestern Myanmar, including the second-biggest city, Mandalay, and the capital Naypyitaw, were struggling to cope with an influx of injured people, the UN Office for the Coordination of Humanitarian Affairs said late on Saturday.

The quake also shook parts of neighbouring Thailand, bringing down an under-construction skyscraper and killing 18 people across the capital, according to Thai authorities.

At least 76 people remained trapped under the debris of the collapsed Bangkok building, where rescue operations continued for a third day, using drones and sniffer dogs to hunt for survivors. (Reuters)