At least 25 people were killed and dozens of buildings destroyed when a strong earthquake struck Myanmar near the Thai border, officials from both countries said.
Tremors were felt as far away as Bangkok, almost 800 kilometres from the epicentre, Hanoi and parts of China during the earthquake on Thursday local time (2.55am today NZST), which the US Geological Survey (USGS) measured at magnitude 6.8.
A Myanmar official warned there could be "many more casualties" in the town of Tarlay, close to the epicentre, as he confirmed 10 men, a boy and 13 women had been killed when the quake struck.
"Five monasteries and 35 buildings collapsed in the town. Those people were killed when the buildings collapsed," said the official, who declined to be named.
Twenty people were injured in Tarlay in the district of Tachileik, and the official said the main road into the area was closed after being damaged in the quake.
Just across the border from Tachileik, Thai authorities said a 52-year-old woman was killed in Mae Sai district after a wall of her house collapsed.
Terrified residents across the region fled their homes, tall buildings swayed and hospitals and schools were evacuated during the tremors.
The quake struck 90 kilometres north of Chiang Rai and 235 kilometres north-northeast of Chiang Mai, Thailand's second city and a popular tourist destination. Tall buildings shuddered in Bangkok during the tremor.
Its epicentre was close to the borders with Thailand and Laos and was just 10 kilometres deep.
Thailand's meteorological department said today it had registered six large aftershocks following the initial quake.
Chiang Rai governor Somchai Hatayatanti told AFP late yesterday that efforts were made to evacuate people from tall buildings and he had ordered all patients from Mae Sai District Hospital to be taken to Chiang Rai.
The shaking was felt throughout China's southwest province of Yunnan, according to state-run China National Radio but no casualties or structural collapses had been reported as of this morning.
However, the earthquake reportedly caused cracks in some homes and schools in and around the rugged Xishuangbanna region which borders Myanmar, and fear of aftershocks forced many people in the area to spend the night outdoors.
Some residents of the Vietnamese capital Hanoi fled their homes in panic when the quake shook the city.
Nguyen Thi Hong Hanh, 36, who lives on the 10th floor of a highrise, said her husband noticed their pet fish shaking in their tank.
"We all rushed to the street. All the other people in the apartments also rushed out," she said.
Hanoi felt the tremor at about magnitude 5.0, according to Dinh Quoc Van, deputy head of the earthquake monitoring department.
The quake comes two weeks after Japan was hit by a monster earthquake, which unleashed a devastating tsunami that left around 27,000 people dead or missing and triggered a crisis at its Fukushima nuclear plant.
No tsunami warning was issued after the Myanmar quake as US seismologists said it was too far inland to generate a devastating wave in the Indian Ocean.
The USGS initially recorded the quake as magnitude 7.0 but later revised it down to 6.8.