"At least two and half million tonnes of debris -- roughly 125,000 truckloads -- must be removed in Myanmar," the UN Development Programme (UNDP) said in a statement, pointing to new data generated by remote sensing data.

Two weeks on from the 7.7-magnitude quake, which killed more than 3,600, the central cities of Mandalay and Sagaing lie devastated, while more than 60,000 people have crowded into temporary displacement sites, the agency said.

They are "too fearful to return to their homes. Transport connectivity is impaired and water supply is not functioning", UNDP's resident representative in the country Titon Mitra warned in the statement.

According to the UNDP analysis, some 1.6 million buildings were located in the areas exposed to the greatest intensity of the quake.

"Many of the exposed buildings were not designed to withstand such powerful seismic activity," the agency said.

It highlighted that more than 10,000 homes and public service buildings may have been significantly damaged or destroyed.

At the same time, 128 health facilities "were exposed to severe or violent tremors, with high likelihood of significant damage or destruction as a result", it said.

"With fewer health facilities to serve the impacted population, concerns are mounting regarding the capacity to provide critical medical care in the aftermath."

Mitra said the UNDP analysis, which integrated advanced satellite data with a range of other data points, presented "a very concerning picture".

"It's critical that we rapidly verify on the ground this view from on high," he said.