About 1,300 people have fled to Thailand as fresh fighting erupted at a border town in eastern Myanmar that has recently been captured by ethnic militants, officials said Saturday.

Fighters from the Karen ethnic minority last week captured the last of the Myanmar army’s outposts in and around Myawaddy, which is connected to Thailand by two bridges across the Moei River. The latest clashes were triggered when the Karen guerillas launched an attack against Myanmar troops who were hiding near the 2nd Thai-Myanmar Friendship Bridge, a major crossing point for trade with Thailand, said police chief Pittayakorn Phetcharat in Thailand’s Mae Sot district.