MAE SOT (Thailand) - ABOUT 20,000 people fled from Myanmar into Thailand to escape fighting between government troops and ethnic rebels following the military-ruled nation's first vote in 20 years, Thai officials said on Tuesday.

At least three civilians were killed when heavy weapons fire hit the town of Myawaddy in Karen State, an official in Myanmar said. There was no information on any troop casualties on either side.

The violence erupted after an election on Sunday that was strongly criticised by the West because of widespread complaints of intimidation and the continued detention of democracy icon Aung San Suu Kyi.

More than 15,000 people had crossed into the Thai town of Mae Sot, fleeing fighting just across the border in Myawaddy, said Samard Loyfar, governor of Tak province in Thailand.

A second pocket of unrest further south pushed some 5,000 people to seek refuge across the border on Monday, said district chief Jamras Srangnoi in Kanchanaburi in Thailand, but many had returned to their homes.

Zipporah Sein, the Thailand-based general secretary of the Karen National Union (KNU), said there had been fighting between government forces and Democratic Karen Buddhist Army (DKBA) troops in the two areas.

20,000 flee clashes