YANGON: Myanmar began releasing hundreds of prisoners on Thursday under a mass amnesty that comes just days before a landmark visit by US President Barack Obama to the formerly military-ruled nation.

Relatives of the scores of political detainees still languishing in jails were waiting anxiously to learn whether they would be among those freed. The government declined to reveal how many dissidents were pardoned.

A prison department official said 452 prisoners would walk free.

“There are some foreigners included in the amnesty,” he added, speaking on condition of anonymity, without giving details of their nationalities. The release was also announced in state media.

Myanmar, formerly known as Burma, has already freed hundreds of political prisoners incarcerated by the former junta, as part of reforms that have led to a dramatic thaw in relations between the one-time pariah nation and the West.

Obama will on Monday become the first sitting US president to visit Myanmar, where he will meet former general President Thein Sein and opposition leader Aung San Suu Kyi.

Suu Kyi, a Nobel Peace Prize winner, was herself released by the regime in 2010 after years under house arrest.

A spokesman for Suu Kyi’s National League for Democracy (NLD) welcomed the latest amnesty but questioned its timing.

“It is strange that they released prisoners just before Obama’s visit…They should have done it before and showed their genuine will to give the amnesty,” Ohn Kyaing said, adding that it was unclear if any NLD members were among those being freed.

The last major amnesty in September saw dozens of dissidents freed just before a historic visit to the United Nations in New York by Thein Sein. But it left many political prisoners behind bars.

As recently as about a year ago, rights groups accused Myanmar of wrongfully imprisoning about 2,000 political opponents, dissidents and journalists.

The visit by Obama—fresh from his re-election victory—has been lauded by Myanmar as a sign of confidence in the reforms introduced under a nominally civilian government, which replaced the junta in March 2011.