YANGON: Myanmar on Tuesday began freeing dozens of its remaining detained activists, officials said, after the country vowed to release all prisoners of conscience by the end of the year.

“Our government will release 56 political prisoners,” presidential adviser Hla Maung Shwe told AFP, in comments confirmed by correctional department officials.

Setting free dissidents detained arbitrarily under the former junta has been a cornerstone of reforms by a new quasi-civilian regime and has been warmly welcomed by the international community with the scrapping of most western sanctions.

Hundreds of political detainees have been freed since President Thein Sein took power in March 2011. But activists say authorities are continuing to prosecute dissidents and scores remain behind bars. They accuse the government of using the headline-grabbing releases for political gain and leverage with the international community.

Thein Sein, who travelled on Tuesday to a meeting of regional powers in Brunei, announced there would be “no prisoners of conscience in Myanmar” by the end of the year during his first visit to London in July.

Numbers for political prisoners held in Myanmar vary, but Aung San Suu Kyi's opposition party said there were around 140 activists held before Tuesday's announcement.

Thet Oo, from the ex-detainees group Former Political Prisoners, told AFP that he could confirm that some of the 56 had already been set free, adding that his organisation estimates that around 50 new activists have been held by the current regime.

“Twenty of them are in the prisons and the rest are facing trials. Most of them were charged for protesting without permission and under charges causing defaming to the state,” he said.

The arbitrary imprisonment of political opponents was a hallmark of the previous brutal junta and sparked a web of western sanctions which stifled the economy.

Since Thein Sein took power, the nation has undergone dramatic change including the election of opposition leader Suu Kyi to parliament.

Myanmar analyst Richard Horsey said the government were still arresting and detaining activists, but said this was “generally in a transparent way unlike the past”.

He said recent detentions have often been in “accordance with a law -- even if it's a law that has provisions that aren't consistent with democratic freedoms”.

“So the key will be, at the end of the year, has Thein Sein met his pledge on having no political prisoners, and how are the more recently arrested people classified?” he said.

Former Political Prisoners, an activist group, said many of those released Tuesday are believed to be from the country's armed ethnic minority groups in northern Kachin and eastern Shan states.

The inclusion of jailed members of the Kachin Independence Army comes amid crucial peace negotiations with the rebels.

As part of the reforms Thein Sein's government has reached tentative peace deals with major armed ethnic minority rebel groups in the country, which has been wracked by civil wars since independence from British colonial rule in 1948.

Myanmar released some 70 political prisoners in July, many of whom were also from Kachin groups, as the detention of ethnic minority rebels weighs on negotiations.