Myanmar will free 452 prisoners, including an unspecified number of dissidents according to the government, in an apparent goodwill gesture days ahead of a historic visit to the former military state by U.S. President Barack Obama, according to Reuters.

State media said the prisoners would be freed with the "intent to help promote goodwill and the bilateral relationship". A Home Ministry official said "prisoners of conscience" would be among them but declined to say how many.

The Assistance Association for Political Prisoners (AAPP) said it was making checks but it had yet to hear of a single political detainee being released.

Over the past year, Myanmar, also known as Burma, has introduced the most sweeping reforms in the former British colony since a 1962 military coup. A semi-civilian government stacked with former generals has allowed elections, eased rules on protests, relaxed censorship and freed some dissidents.

The United States has called for the release of all remaining political prisoners but Myanmar has failed to do that.

About 700 were freed between May 2011 and July 2012. An amnesty was announced in September but it included only 88 dissidents, the AAPP said, leaving several hundred behind bars.

Obama will become the first U.S. president to visit Myanmar when he travels there during a November 17-20 tour of Southeast Asia that will also take in Thailand and Cambodia.