YANGON (Reuters) - Myanmar's government has freed 23 political prisoners, a senior interior ministry official said on Friday, the day President Thein Sein was due to leave for a landmark visit to the United States.
The official declined to be identified and would not provide the names of those released or give further details.
A member of the 88 Generation Open Society, a pro-democracy activist group, said 10 prisoners had been released from Insein Prison in Yangon, notorious for the harsh treatment of detainees under the military regime that ruled Myanmar almost for half a century.
Thein Sein took over at the head of a quasi-civilian government in March 2011 and has freed hundreds of political prisoners as part of sweeping political and economic reforms.
However, activist groups say hundreds more remain behind bars and have accused the government of cynically freeing prisoners in waves at strategic diplomatic moments, for example when Western countries are about to review economic sanctions imposed on the former junta.
Thein Sein is due to meet U.S. President Barack Obama on Monday. Obama became the first serving U.S. leader to visit the country, which is also known as Burma, in November last year and dozens of detainees were freed on the day he arrived.
"The release of any political prisoner is welcome, but two years after the reform process began, people should be asking why there are still hundreds of political prisoners still in jail," Wai Hnin, campaign officer at Burma Campaign UK, said in a statement.
The most recent release of prisoners was in late April, when Thein Sein announced an amnesty for about 100 prisoners, including 56 considered political detainees, a day after the European Union lifted most of its sanctions on the country.
Before that, more than 800 political prisoners were freed in amnesties between May 2011 and November 2012, according to the Assistance Association for Political Prisoners (AAPP).
As of May 11, its website listed the names of 183 people it called political prisoners and whose whereabouts it had verified.
Embassies and other groups give different figures. The government, which has in the past rejected the term "political prisoner", has recently set up a Committee to Scrutinise Remaining Prisoners of Conscience, including pro-democracy activists, to examine the issue.
Reporting by Aung Hla Tun; Writing by Alan Raybould; Editing by Robert Birsel