By Aung Hla Tun
YANGON (Reuters) - Myanmar pardoned more than 500 prisoners on Monday in an amnesty that included political detainees, according to the opposition party, a step that could strengthen the former military state's growing bonds with Washington.
A government bulletin announcing the news on state television did not make clear if any of those affected were political inmates. But Naing Naing, an official of Aung San Suu Kyi's National League for Democracy (NLD) party, said he was hopeful the amnesty included the country's 424 remaining political prisoners.
"We're optimistic that these are the remaining political prisoners," said Naing Naing, himself a former political prisoner.
The NLD, he added, received word of the freed political prisoners from the Assistance Association for Political Prisoners (AAPP), a Thai-based group that tracks prisoners in Myanmar, also known as Burma.
Contacted by Reuters, Bo Kyi, secretary-general of the AAPP, said political prisoners were among those who had been released but the organization needed more time to confirm the number.
The timing of the amnesty is significant, coming days ahead of a visit to the United States by Myanmar's reformist President, Thein Sein, and a separate U.S. trip that began on Monday by opposition leader Suu Kyi, the Nobel Peace Prize winner.
Her election to parliament in April helped to transform Myanmar's pariah image and convince the West to begin rolling back sanctions after a year of dramatic reforms, including the release of about 700 political prisoners in amnesties between May 2011 and July this year.
The United States has repeatedly called for all remaining dissidents to be freed as a pre-condition for further economic rewards, including a relaxation of a ban on imports of Myanmar-made products imposed years ago in response to human rights abuses.
Naing Naing of the NLD said the 424 freed political prisoners excluded inmates who were former military intelligence officials purged under the military junta that ruled for 49 years as one of Asia's most oppressive regimes before ceding power to a semi-civilian government in March last year.
Suu Kyi left Sunday for the United States where she will receive a Congressional medal.
Thein Sein, a former general, was due to head to the United States on September 24, where he will address the United Nations General Assembly in New York for the first time as president.
(Writing by Jason Szep; Editing by Nick Macfie)