A 7.7 magnitude earthquake rocked Thailand and neighboring Myanmar midday on Friday, causing the collapse of a high-rise building under construction in Bangkok and forcing hundreds of thousands to evacuate from their homes and workplaces.

The midday temblor was followed by a strong 6.4 magnitude aftershock.

Thailand’s Prime Minister Paetongtarn Shinawatra said at least three were confirmed dead in the building that collapsed after the massive earthquake. Emergency responders said an unknown number of others are still under the rubble.

Rescue worker Songwut Wangpon told reporters another seven people had been found alive, as he spoke outside the tall pile of rubble that was once a high-rise building under construction.

A dramatic video circulated on social media showing the multi-story building with a crane on top collapsing into a cloud of dust, while onlookers screamed and ran.

An AFP photographer at the site saw ambulances and rescue teams at the site, which is near the city’s sprawling Chatuchak market, a popular destination for tourists and locals alike.

“When I arrived to inspect the site, I heard people calling for help, saying ‘help me,'” Worapat Sukthai, deputy police chief of Bang Sue district, told AFP. “We estimate that hundreds of people are injured but we are still trying to determine the number of casualties.”

People in Bangkok evacuated from their buildings were cautioned to stay outside in case there were more aftershocks.

The US Geological Survey and Germany’s GFZ center for geosciences said the earthquake was a shallow 10 kilometers (6.2 miles), with an epicenter in Myanmar, according to preliminary reports.

“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 Morton, thousands of people poured into Benjasiri Park from nearby shopping malls, high rises, and apartment buildings along Bangkok’s busy Sukhumvit Road.

Many were on phones trying to reach loved ones as others sought shade from the hot early afternoon sun. Others stared up fearfully at the tall buildings in the densely packed part of the city.

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

The sound of sirens echoed throughout central Bangkok and vehicles filled the street, leaving some of the city’s already congested streets gridlocked. The elevated rapid transit system and subway were shut down.

City Hall declared the city a disaster area to facilitate interagency aid and emergency help.

Paul Vincent, a tourist visiting from England, was at a street-side bar when the quake struck.

“The next thing, everybody came on the street, so there was a lot of screaming and panicking, which obviously made it a lot worse,” he said.

As he came onto the street himself, he said he saw a high-rise building swaying and water was falling from a rooftop pool.

“When I saw the building, oh my God, that’s when… it hit me,” he said. “There were people crying in the streets and, you know, the panic was horrendous really.”

In Mandalay, Myanmar’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.

At least three people died after a mosque partially collapsed in the town of Taungnoo in Bago region, two eyewitnesses told Reuters.

“We were saying prayers when the shaking started… Three died on the spot,” said one of the people who spoke to Reuters.

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.

Residents in Yangon rushed out of their homes when the quake struck. There were no immediate reports of injuries or deaths.

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

AFP journalists saw the entrance of the emergency department at the city’s main hospital pancaked onto a car.

Wounded at the 1,000-bed facility were being treated outside, intravenous drips hanging from their gurneys. Some writhed in pain, others lay still as relatives sought to comfort them.

A hospital official ushered journalists away, saying: “This is a mass casualty area.”

Another official said hundreds of injured people had arrived at the facility.

“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 route to the hospital was jammed with vehicles. An ambulance tried to make its way through, a paramedic shouting, “Cars, move aside so the ambulance can get through.”

At the city’s National Museum, pieces fell from the ceiling as the building began shaking. Uniformed staff ran outside, some trembling and tearful, others grabbing cellphones to try to contact loved ones.

To the northeast, the earthquake was felt in Yunnan and Sichuan provinces in China and caused damage to houses and injuries in the city of Ruili on the border with Myanmar, according to Chinese media reports.

Videos that one outlet said it had received from a person in Ruili showed building debris littering a street and a person being wheeled in a stretcher toward an ambulance.

The shaking in Mangshi, a Chinese city about 100 kilometers (60 miles) northeast of Ruili, was so strong that people couldn’t stand, one resident told The Paper, an online media outlet.

A resident of Kunming, the provincial capital of Yunnan, told The Paper that her ceiling lamp was swinging wildly and the shaking lasted more than 10 seconds.

In Bangkok, alarms went off in buildings as the earthquake hit around 1:30 p.m., and startled residents were evacuated down staircases of high-rise condominiums and hotels.

The greater Bangkok area is home to more than 17 million people, many of whom live in high-rise apartments.

Water from high-rise rooftop pools sloshed over the side as they shook, and debris fell from many buildings as the long-lasting earthquake rattled the city.

“I have experienced earthquakes twice before in Myanmar, but that was only one second, one big bang, but here it went on for at least, I’d say a minute,” said Zsuzsanna Vari-Kovacs, a Hungarian resident of Bangkok, who had just finished eating at a restaurant when the quake hit. “My husband was in a high-rise, I think that’s even worse.”

Thailand’s Department of Disaster Prevention said the quake was felt in almost all regions of the country.

Shinawatra called an emergency meeting to assess the impact of the quake. Myanmar’s ruling junta made a rare request for international humanitarian aid and declared a state of emergency across six regions after the quake.