By Aung Hla Tun
YANGON (Reuters) - Myanmar released prisoners on Thursday in a goodwill gesture ahead of a historic visit to the former military state by U.S. President Barack Obama, but activists and the main opposition party said there seemed to be no political detainees among them.
State media said early in the day that 452 prisoners would be freed with the "intent to help promote goodwill and the bilateral relationship". A Home Ministry official said some "prisoners of conscience" would be among them.
However, the National League for Democracy party of Nobel laureate Aung San Suu Kyi said that was not the case.
"It's so disappointing that none of those freed today are political prisoners," said senior party official Naing Naing, himself a former detainee.
Myanmar has released about 800 political prisoners as part of a dramatic reform program over the past year and a half but it is believed to be still holding several hundred.
The prisoners released on Thursday included people who had been jailed for deserting the army or committing some other military offence, Naing Naing said. "Maybe these people are political prisoners by their yardstick."
The Assistance Association for Political Prisoners (AAPP) had not heard of any political prisoners being among the 144 people it said had been released by mid-afternoon.
Families are often told by the authorities to prepare for the release of prisoners who can be in jails in distant provinces, but AAPP representative Bo Kyi said he was not aware of any being given such notice on this occasion.
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.
He is due to meet President Thein Sein on Monday but the U.S. president risks criticism for rewarding the new government too soon, especially with political prisoners still behind bars and after security forces failed to prevent ethnic violence in the west of the country last month.
"The manipulative use of prisoner releases just before key international moments is getting more blatant than ever," said Mark Farmaner of the London-based advocacy group Burma Campaign UK.
It, too, had not been able to confirm the release of any political prisoners. "At some point the international community will have to start asking why Thein Sein has decided to keep hundreds of other political prisoners in jail," Farmaner said.
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.
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.
The United States has called for the release of all political prisoners.
International human rights activists met senior White House officials in Washington this week to press Obama to take a tough line with leaders in both Myanmar and Cambodia during his Southeast Asia tour.
The election of democracy champion Aung San Suu Kyi, a former political prisoner, to parliament in April helped to transform Myanmar's pariah image and persuade the West to begin rolling back sanctions after a year of reforms.
The United States eased sanctions on Myanmar this year in recognition of the political and economic change, and many U.S. companies are looking at starting operations in the country located between China and India, with its abundant resources and low-cost labor.
Obama has sought to consolidate ties and reinforce U.S. influence across Asia in what officials have described as a policy "pivot" toward the region as wars in Iraq and Afghanistan wind down.
Myanmar grew close to China during its decades of isolation, reinforced by Western sanctions over its poor human rights record, but it is now seeking to expand relations with the West.
On Tuesday, about half a dozen human rights activists took part in the talks at the White House, which included Samantha Power, a top Obama adviser and outspoken expert on genocide.
Power, considered a "humanitarian hawk" within the administration, wrote a blog on the White House website last week signaling that Obama would use the Myanmar trip to put pressure on the government to do more on human rights.
The activists left the White House meeting satisfied that Obama intended to push hard on human rights and political and economic reform in closed-door talks with the Myanmar president and in his public remarks, including a speech.
(Additional reporting by Andrew R.C. Marshall and Paul Carsten in Bangkok; Writing by Jason Szep and Alan Raybould; Editing by Robert Birsel)