A huge 7.7 magnitude earthquake has hit central Myanmar, according to the United States Geological Survey (USGS).

The epicentre was 16km (10 miles) north-west of the city of Sagaing, at a depth of 10km, sending strong tremors that were felt as far as south-west China and Thailand.

At least 81 construction workers are missing after an unfinished high-rise building collapsed hundreds of miles away in Bangkok, according to Thailand’s deputy prime minister.

A rescuer in Mandalay, Myanmar’s second-largest city, told the BBC the damage is “enormous”, and the number of casualties is “at least in the hundreds”.

There have been reports of roads buckling in the capital of Naypyidaw, and the country’s military government has declared a state of emergency in six regions.

The earthquake struck near Mandalay, which has a population of about 1.5 million people.

A second quake struck 12 minutes after the first, according to the USGS, with a magnitude of 6.4 and its epicentre was 18km (11.1 miles) south of Sagaing.

Soe Lwin, in Myanmar’s largest city, Yangon, said he felt the first earthquake for a “long time” and added that residents are worried about the potential for more aftershocks.

Bui Thu, a BBC journalist who lives in Bangkok, told the BBC World Service’s Newsday programme that she was at home cooking when the initial quake happened.

“I was very nervous, I was very panicked,” she said.

“Buildings in Bangkok are not engineered for earthquakes, so I think that’s why I think there’s going to be big damage.”

Myanmar has been in political turmoil since a military junta seized power in a 2021 coup.

The state controls almost all local radio, television, print and online media, and Internet use is restricted in the country, which often makes access to information difficult.