Myanmar, Thailand earthquake deadliest in 100 years: 23 killed, dozens trapped in Bangkok high-rise collapse | Top updates

Rescuers work at the site of a high-rise building under construction that collapsed after a 7.7 magnitude earthquake in Bangkok, Thailand.

A massive earthquake struck Myanmar on Friday, killing at least 20 people, and dozens trapped in neighbouring Thailand where an under-construction 30-storey skyscraper collapsed. The midday temblor with an epicentre near Mandalay, Myanmar's second largest city, was followed by a strong 6.4 magnitude aftershock, toppling buildings, rupturing roads and collapsing the well-known Ava bridge.

A dramatic video of the building's collapse near Bangkok's popular Chatuchak market circulated on social media showed the multi-story building with a crane on top toppling into a cloud of dust, while onlookers screamed and ran. Elsewhere, people in Bangkok evacuated from their buildings were cautioned to stay outside in case there were more aftershocks.

The devastation prompted a rare request for international aid from Myanmar's isolated military junta, which has lost swathes of territory to armed groups, as it declared a state of emergency across the six worst-affected regions. With the country in the midst of a prolonged bloody civil war, it was not clear how help would get to many regions.

Hundreds of casualties were taken to a hospital in the capital Naypyidaw, with the wounded being treated outside because of damage to the building. The emergency department's entrance had collapsed on top of a car.

A hospital official ushered journalist away, saying: "this is a mass casualty area." "I haven't seen (something) like this before. We are trying to handle the situation. I'm so exhausted now," a doctor told AFP.

The rare plea from the junta raises the prospect that damage and casualties may be on a large scale, with Myanmar's medical system and infrastructure ravaged by four years of civil war.

Updating on the building collapse in Bangkok, Deputy PM Phumtham Wechayachai told reporters that at least three workers had been killed and 81 more were trapped inside. However, the country’s defence minister later said that 90 people were missing.

Meanwhile, Thai Prime Minister Paetongtarn Shinawatra declared an emergency zone in Bangkok, where some metro and light rail services were suspended, further snarling the city's already notorious traffic. Airports were operating as normal.

The quake was felt across the region, with China, Cambodia, Bangladesh and India all reporting tremors.

Earthquakes are relatively common in Myanmar, where six strong quakes of 7.0 magnitude or more struck between 1930 and 1956 near the Sagaing Fault, which runs north to south through the centre of the country, according to the United States Geological Survey (USGS).

(With inputs from agencies)