Burma has freed at least 20 political prisoners as part of a general amnesty the government says is aimed at promoting “national unity.”

The state-run New Light of Myanmar says 46 prisoners were released Tuesday, under an order by President Thein Sein. It also says 34 foreign prisoners were deported.

Activists say among those released was student protester Aye Aung, who was given a 59-year sentence for distributing pamphlets and participating in a 1998 pro-democracy uprising.

Burma has released hundreds of political prisoners – including several prominent dissidents – since a nominally civilian government came to power last year, ending decades of harsh military rule.

Rights groups remain concerned about the hundreds of prisoners of conscience who are still in detention. Khin Ohmar, the coordinator of Burma Partnership, tells VOA she is worried that many less-prominent activists may be forgotten.

“Those more than 400 political prisoners still behind bars, because they are not prominent, that's why they need more attention from the international community, including the United States and the rest of the world and international governments. They must all work together and keep calling on this regime and pressuring them to release these remaining political prisoners without further delay, unconditionally.”

Many Western governments have begun relaxing sanctions against Burma in response to its political and economic reforms. But the unconditional release of all remaining political prisoners remains a key condition for many to fully restore ties with the once-isolated nation.

Pro-democracy leader Aung San Suu Kyi says her National League for Democracy Party has counted at least 330 political prisoners still detained, although many rights groups put the figure much higher.

The government says the remaining dissidents have not been released because authorities are working to determine those who are guilty of committing violent crimes and those who are activists.

In addition to releasing political prisoners, Burma's government has also relaxed media censorship, sought cease-fires with armed rebel groups,and permitted the once-imprisoned Aung San Suu Kyi to successfully run for parliament.