A powerful 7.7 magnitude earthquake has hit Myanmar and Thailand, with a state of emergency declared and fears of mass casualties after tremors shook high-rise buildings and destroyed apartment blocks.

The US Geological Survey and Germany’s GFZ centre for geosciences said the quake struck at a shallow 6.2 miles below the surface, before a second quake, with a magnitude of 6.4, shook the area 12 minutes later.

The force of the tremors caused a mosque in the city of Mandalay, close to the epicentre of the quake, to collapse, with at least ten worshippers said to have been killed.

Officials at a major hospital in Myanmar’s capital Naypyidaw have declared it a ‘mass casualty area’, with the death toll in the country expected to rise after buildings were toppled and debris was sent flying.

Large parts of neighbouring Thailand also felt the quake, with a state of emergency declared in the country’s capital, which is home to more than 17 million people, many of whom live in high-rise apartments.

Shocking video has shown the moment workers fled as a building under construction collapsed as it was shaken by the force of the quake. 

At least three people have been killed and dozens of workers rescued from under the rubble of the skyscraper, Thai authorities said. Local media has reported that some 43 workers were missing after the collapse.

Alarms went off in buildings as the earthquake hit around 1.30pm local time, and startled residents were evacuated down staircases of high-rise buildings and hotels in densely populated central Bangkok.

They remained in the streets, seeking shade from the midday sun in the minutes after the quake.

The quake was forceful enough to send water sloshing out of pools, some high above the street in high-rises, as the tremor shook.

Witnesses in Bangkok said people ran out onto the streets in panic, many of them hotel guests in bathrobes and swimming costumes as water cascaded down from an elevated pool at a luxury hotel. 

‘All of a sudden the whole building began to move, immediately there was screaming and a lot of panic,’ said Fraser Morton, a tourist from Scotland, who was in one of Bangkok’s many malls shopping for camera equipment.

‘I just started walking calmly at first but then the building started really moving, yeah, a lot of screaming, a lot of panic, people running the wrong way down the escalators, lots of banging and crashing inside the mall.’

Like thousands of others in downtown Bangkok, Morton sought refuge in Benjasiri Park – away from the tall buildings all around.

‘I got outside and then looked up at the building and the whole building was moving, dust and debris, it was pretty intense,’ he said. ‘Lots of chaos.’

The earthquake hit Myanmar as it is in the grips of a civil war.

At a 1,000-bed general hospital in the country’s capital, rows of wounded were treated outside the emergency department, some writhing in pain, others lying still as relatives sought to comfort them.

In Mandalay, the country’s second-largest city and close to the epicenter, the earthquake damaged part of the former royal palace and buildings, according to videos and photos released on Facebook social media.

While the area is prone to earthquakes, it is generally sparsely populated, and most houses are low-rise structures.

In the Sagaing region just southwest of Mandalay, a 90-year-old bridge collapsed, and some sections of the highway connecting Mandalay and Myanmar’s largest city, Yangon, were also damaged.

In Naypyitaw, the quake damaged religious shrines, sending parts toppling to the ground, and some homes. 

The quake damaged buildings in Bangkok and forced the suspension of some metro and light rail services in the city.

Thai Prime Minister Paetongtarn Shinawatra said on Friday she had interrupted an official visit to the southern island of Phuket to hold an ‘urgent meeting’ after the quake, according to a post on X.

Tremors were also felt in China’s southwest Yunnan province, according to Beijing’s quake agency, which said the jolt measured 7.9 in magnitude.

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 USGS.

A powerful 6.8-magnitude earthquake in the ancient capital Bagan in central Myanmar killed three people in 2016, also toppling spires and crumbling temple walls at the tourist destination.

The breakneck pace of development in Myanmar’s cities, combined with crumbling infrastructure and poor urban planning, has also made the country’s most populous areas vulnerable to earthquakes and other disasters, experts say.

The impoverished Southeast Asian nation has a strained medical system, especially in its rural states.