Bangkok, Thailand (CNN) -- Myanmar's military rulers marked the country's independence day by commuting sentences and apparently releasing more than 30 prisoners, but opposition activists said Wednesday that the moves were unsatisfactory.
The United States also urged the nation to make greater efforts to improve its human rights record.
A decree by President Thein Sein, published Tuesday in a state-run newspaper, grants amnesty to prisoners "for the sake of state peace and stability, the rule of law, national consolidation" and humanitarian grounds. It reduces death sentences to life imprisonment; cuts sentences longer than 30 years down to 30; limits terms of 20-30 years to 20 years; and reduces shorter prison terms by 25%.
Myanmar, also known as Burma, marks its 1948 independence from Britain on Wednesday. The southeast Asian country has been ruled by a military junta since 1962, and the generals have come under criticism for their human rights record in recent years. Sein, a former military official and prime minister, became president last year after an election criticized by democracy activists as a sham.
Among the prisoners are more than 1,500 dissidents convicted of criminal charges over the years, including Buddhist monks and some journalists, according to the Assistance Association for Political Prisoners (AAPP), a nonprofit organization based in Thailand that supports and advocates on behalf of political prisoners in Myanmar.
"We have received information from Myanmar there are about 33 prisoners released yesterday," Aung Myo Thein, a spokesman for AAPP, said Wednesday. But he added that none of those released appeared to be high-profile detainees.
He said the actions by the government were not enough, noting that some political prisoners had merely had sentences of more than 100 years reduced to 60 years.
The National League of Democracy, led by Nobel laureate Aung San Suu Kyi, said it was unclear how many of its jailed members may have been freed following Tuesday's announcement.
"At this stage, we received reports that there are about two to three NLD members" released, Tin Oo, vice chairman of NLD, said Wednesday.
But he said that the measures did not constitute a "real amnesty," since they just entailed the reduction of sentences, with most of those released not political prisoners.
Myanmar released about 200 political prisoners along with more than 6,000 other inmates in October. But the AAPP called the move "disingenuous" and "unsatisfactory," noting that many prominent dissidents remained behind bars.
The United States has tried to encourage an opening with Myanmar in recent years. Secretary of State Hillary Clinton made a trip there in November, and the Obama administration has built a policy of what it calls "parallel engagement" with the junta as well as the opposition.
U.S. State Department spokeswoman Victoria Nuland told reporters Tuesday that more prisoners needed to be released before Washington will take "significantly more steps towards normalization."
"From that perspective, it's not a step of the magnitude that we would be interested in matching," she said.