BANGKOK (AP) — A powerful earthquake rocked Myanmar on Friday, causing extensive damage across a wide swath of one of the world’s poorest countries and prompting officials to warn that the initial death toll — above 140 — was likely to grow in the days ahead. In neighboring Thailand, at least six died in Bangkok, where a high-rise under construction collapsed.

The full extent of death, injury and destruction was not immediately clear — particularly in Myanmar, which is embroiled in a civil war, and where information is tightly controlled.

“The death toll and injuries are expected to rise,” the head of Myanmar’s military government, Senior Gen. Min Aung Hlaing said as he announced on television that at least 144 people were killed and 730 others were injured in his country.

In Thailand, authorities in Bangkok said six people were killed, 22 were injured and 101 were missing from three construction sites, including the high-rise. They revised the death toll Saturday morning from 10 reported the previous day, saying several critically injured people were mistakenly reported dead. Bangkok Governor Chadchart Sittipunt said that more people were believed to be alive in the wreckage as search efforts continued Saturday morning.

The 7.7 magnitude quake struck at midday, with an epicenter near Mandalay, Myanmar ’s second-largest city. Aftershocks followed, one of them measuring a strong 6.4 magnitude.

Myanmar is in an active earthquake belt, though many of the temblors happen in sparsely populated areas, not cities like those affected Friday. The U.S. Geological Survey, an American government science agency, estimated that the death toll could top 1,000.

In Mandalay, the earthquake reportedly brought down multiple buildings, including one of the city’s largest monasteries. Photos from the capital city of Naypyidaw showed rescue crews pulling victims from the rubble of multiple buildings used to house civil servants.

Rescue teams head to Myanmar

Myanmar's government said blood was in high demand in the hardest-hit areas. In a country where prior governments sometimes have been slow to accept foreign aid, Min Aung Hlaing said Myanmar was ready to accept assistance.

A 37-member team from the Chinese province of Yunnan reached the city of Yangon early Saturday with earthquake detectors, drones and other supplies, the official Xinhua news agency reported.

Russia’s emergencies ministry dispatched two planes carrying 120 rescuers and supplies, according to a report from the Russian state news agency Tass. India sent a search and rescue team and a medical team as well as blankets, tarpaulin, hygiene kits, sleeping bags, solar lamps, food packets and kitchen sets, the country’s foreign minister posted on X. Malaysia's foreign ministry said the country will send 50 people on Sunday to help identify and provide aid to the worst-hit areas.

The United Nations allocated $5 million to start relief efforts. President Donald Trump said Friday that the U.S. was going to help with the response, but some experts were concerned about this effort given his administration’s deep cuts in foreign assistance.

But amid images of buckled and cracked roads and reports of a collapsed bridge and a burst dam, there were concerns about how rescuers would even reach some areas in a country already enduring a humanitarian crisis.

“We fear it may be weeks before we understand the full extent of destruction caused by this earthquake," said Mohammed Riyas, the International Rescue Committee’s Myanmar director.

Bridge and monastery collapse and dam bursts in Myanmar

Myanmar's English-language state newspaper, Global New Light of Myanmar, said five cities and towns had seen building collapses and two bridges had fallen, including one on a key highway between Mandalay and Yangon. A photo on the newspaper’s website showed wreckage of a sign that read “EMERGENCY DEPARTMENT," which the caption said was part of the capital’s main 1,000-bed hospital.

Elsewhere, video posted online showed robed monks in a Mandalay street, shooting their own video of the multistory Ma Soe Yane monastery before it suddenly fell into the ground. It was not immediately clear whether anyone was harmed. Video also showed damage to the former royal palace.

Christian Aid said its partners and colleagues on the ground reported that a dam burst in the city, causing water levels to rise in the lowland areas.

Residents of Yangon, the nation's largest city, rushed out of their homes when the quake struck. In Naypyitaw, some homes stood partly crumbled, while rescuers heaved away bricks from the piles of debris. An injured man reclined on a wheeled stretcher, while another man fanned him in the heat.

In a country where many people already were struggling, “this disaster will have left people devastated,” said Julie Mehigan, who oversees Christian Aid’s work in Asia, the Middle East and Europe.

“Even before this heartbreaking earthquake, we know conflict and displacement has left countless people in real need,” Mehigan said.

Myanmar's military seized power from the elected government of Aung San Suu Kyi in February 2021, and is now involved in a bloody civil war with long-established militias and newly formed pro-democracy ones.

Government forces have lost control of much of Myanmar, and many places are incredibly dangerous or simply impossible for aid groups to reach. More than 3 million people have been displaced by the fighting and nearly 20 million are in need, according to the United Nations.

Bangkok building collapsed in a cloud of dust

In Thailand, a 33-story building under construction crumpled into a cloud of dust near Bangkok’s popular Chatuchak market, and onlookers could be seen screaming and running in a video posted on social media. Vehicles on a nearby freeway came to a stop.

Sirens blared across the Thai capital's downtown as a rescuers streamed to the wreckage. Above them, shredded steel and broken concrete blocks, some stacked like pancakes, rose in a towering heap. Injured people were rushed away on gurneys, and hospital beds were also wheeled outside onto a sidewalk.

“It’s a great tragedy," Deputy Prime Minister Suriya Juangroongruangkit said after viewing the site.

Earthquakes are rarely felt in the Bangkok metropolitan area, home to more than 17 million people, many of whom live in high-rise apartments.

Voranoot Thirawat, a lawyer working in central Bangkok, said she first realized something was wrong when she saw a light swinging back and forth. Then she heard the building creaking, and she and her colleagues fled down 12 flights of stairs.

“In my lifetime, there was no earthquake like this in Bangkok,” she said.

Fraser Morton, a tourist from Scotland, was in one of Bangkok’s many malls when the quake struck.

“All of a sudden, the whole building began to move. Immediately, there was screaming and a lot of panic,” he said. Some people fled down upward-moving escalators, he said.

Nearby, Paul Vincent, a tourist visiting from England, recalled seeing a high-rise building swaying, water falling from a rooftop pool and people crying in the streets.

The U.S. Geological Survey and Germany’s GFZ center for geosciences said the earthquake was a shallow 10 kilometers (6.2 miles), according to preliminary reports. Shallower earthquakes tend to cause more damage.

Injuries reported in China

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

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.

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Adam Schreck, Haruka Naga, Jerry Harmer, Grant Peck and Penny Wang in Bangkok, Jamey Keaten in Geneva, Ken Moritsugu in Beijing, Edith M. Lederer and Farnoush Amiri at the United Nations and Jennifer Peltz in New York contributed to this report.