At least two people were killed in a bomb blast on Friday at a market in the town of Myawaddy opposite Tak province.
The explosion occurred in a region where ethnic Karen fighters are battling the government near the border with Thailand.
This busy town is opposite Mae Sot district of Tak province.
The blast also destroyed houses and market shops there.
Burma has been hit by several bomb blasts in recent years, which the junta has blamed on armed exile groups or ethnic rebels.
The bomb went off one day before the anniversary of the popular uprising in Burma, known as 8/8/88, which ended after about hundreds were killed and thousands others wounded in a bloody military crackdown.