President Thein Sein ordered their release just ahead of a forum in Brunei to be attended by leaders from across Southeast Asia and the Pacific. Burma is expected to face questions about ongoing sectarian violence.
It has become a pattern for prisoner amnesties in Burma to coincide with high-profile international meetings as a way of highlighting the nominally civilian government's reforms since taking office after years of absolute military rule.
A member of the government's political prisoner scrutiny committee, Ye Aung, said those released included several ethnic minorities. About 130 political prisoners are still believed to be in jail.
Burma's decades-long refusal to free activists was the main justification for years of Western sanctions against the country.