BANGKOK - A strong and shallow earthquake rattled northern Thailand on Monday afternoon, shaking tall buildings in Bangkok hundreds of miles to the south.
The 6.0-magnitude quake, at a depth of just 7.4 kilometres (4.5 miles), hit just after 6 pm (1100 GMT), the US Geological Survey said.
The epicentre was around 27 kilometres from the mountainous city of Chiang Rai.
As darkness fell a Thai official warned residents in Chiang Rai province to brace for aftershocks.
"This is the most powerful earthquake to strike the country in recent times," Burin Wechbunthung, a seismologist at the Meteorological Department, told AFP.
"There have been five aftershocks so far and people within a 150-kilometre radius of the epicentre in Phan district should be warned," he added.
There were no immediate reports of major damage, although television showed cracked building facades, broken shop windows and damage to roads.
The area is a remote mountain retreat near the border with Myanmar and Laos and popular with foreign tourists.
Another official from the Meteorological Department said the quake had a 6.1-magnitude.
"The earthquake occurred on the Phayao fault line. This fault line covers Phayao and Chiang Rai provinces. Officials are checking how bad the damage is," Sophon Chaiya told reporters.
The quake was felt in the nearby city of Chiang Mai and as far south as Bangkok, 800 kilometres (500 miles) away, where tall buildings shook for several seconds.
It was also felt in Myanmar's commercial centre of Yangon, an AFP reporter there said.
Major earthquakes are rare in Thailand, although tremors often strike the north of the country.
A 6.8-magnitude quake hit Myanmar's eastern state of Shan in March 2011, leaving dozens dead near the border with Thailand and Laos and reducing homes and government buildings to rubble.
The area hit in 2011 is close to Chiang Rai and prompted the then-government to call for a review of Thailand's preparedness for a major seismic event.
Chiang Rai province is dotted with national parks which draw droves of tourists, many of them travelling from the nearby city of Chiang Mai.