Myanmar is releasing more than 14,600 prisoners under a clemency program that will include very few political prisoners.
Prison Department Director General Zaw Win said most of the convicts, including 2,166 women, would be freed Tuesday from jails around the country.
The limited nature of the program - which commutes death sentences to life imprisonment and cuts one year from other convicts' prison terms - has drawn criticism from many who had expected more generous terms, similar to broader amnesties that have been announced in the past.
New York-based Human Rights Watch issued a statement calling the clemency "a pathetic response to international calls for the immediate release of all political prisoners."
"For the 2,100 political prisoners unjustly serving sentences of up to 65 years, the one-year reduction is a sick joke," the rights group said Tuesday.
The Myanmar government generally grants amnesties to mark important national days. The last in 2009 freed 7,114 prisoners. Most recipients are petty criminals, but previous mass releases have usually included a handful of political detainees.
Most of the country's political prisoners, both from the pro-democracy movement and from out-of-favor factions in the government, are serving long sentences that will keep them locked up.
"My hopes are shattered. I thought my husband would be released in a general amnesty," said Moe Moe, 33, the wife of a former military intelligence officer sentenced in 2005 to 15 years in prison, after the measure was announced Monday night.
Asked how many political prisoners were among those to be released, Zaw Win repeated the government's position that the country has no political detainees.
But he said "some prisoners who are charged under emergency laws and for links with illegal organizations will be among those freed." Emergency laws are broadly defined security statutes usually used to prosecute political activists, who are often accused of links to banned political groups.
Long-term detainees include prominent student activists such as Min Ko Naing who are serving 65-year prison sentences and politicians from ethnic minority parties such as Shan leader Hkun Htun Oo who have sentences of more than 80 years.
Apart from pro-democracy activists, many former intelligence officers who were on the losing side of a power struggle are serving lengthy prison sentences.
Former Prime Minister and military intelligence chief Khin Nyunt, who is serving a 44-year sentence under house arrest, is not benefiting from the clemency program, Zaw Win told reporters at Yangon's Insein Prison, where he gave a speech to inmates.
U.S. State Department spokesman Mark Toner said in Washington that the U.S. reiterated its call that all political prisoners be released immediately.
An amnesty had been expected when the country held its first elections in 20 years in November, when parliament convened in January, and then when the nominally civilian government was sworn in at the end of March.
Myanmar has more than 60,000 prisoners in 42 prisons and 109 labor camps.
Zaw Win said 2,600 of the more than 8,000 inmates at Insein Prison were being released. He said 348 prisoners on death row will have their sentences commuted to life imprisonment.
Myanmar has been under the sway of the army since 1962, and critics say its recent transition to civilian rule is a charade that perpetuates military rule.