Burma's government on Monday pardoned more than 500 prisoners, among them political detainees and some foreigners.
An official announcement described the move as an effort to "bring tranquillity and perpetual peace" to the country. The move comes a week before Burmese President Thein Sein is set to travel to the United States to attend the United Nations General Assembly session.
It also comes on the same day the U.S.-based group Human Rights Watch criticized Burma for its failure to release all remaining political prisoners and for imposing restrictions on those who have been freed.
It is unclear how many of those released are political prisoners, but Thein Sein has made the release of such detainees the centerpiece of his reform policies.
Burma's democratic opposition party, the National League for Democracy, estimates there are about 300 political prisoners still in jail. But other activists contend there are at least 100 more than that.
In Washington, the State Department reacted cautiously to news of the amnesty. A spokeswoman urged Burma's government to free all remaining political prisoners.
Some information for this report was provided by AP and Reuters.