A 1,000-bed hospital in Myanmar capital Naypyidaw is a likely "mass casualty area", reports said on Friday after a 7.7 magnitude earthquake struck near the city of Sagaing, which is 260km away.

At least 20 deaths have been confirmed from the hospital so far, but doctors there said (on condition of anonymity) they expect the toll to rise rapidly into the hundreds. Scenes from outside the building showed injured people being treated on the streets, with intravenous drips hanging from gurneys as family and loved ones comforted them. "I haven't seen (something) like this before. We are trying to handle it but I'm so exhausted," a doctor said.

"A stream of casualties" were spotted arriving at the hospital, which itself was heavily damaged; a car was crushed under the heavy concrete of its fallen entrance, reports said.