YANGON (AFP) ― Myanmar has agreed to release some 70 political prisoners, an official said Tuesday, after President Thein Sein vowed to free all dissidents by the end of the year.

The move, the latest gesture of reform by the former general who has ushered in a period of sweeping change in the country, was greeted with caution by activists concerned that authorities are continuing to prosecute dissidents.

“The president has signed an amnesty for about 70 political prisoners around the country,” presidential adviser Hla Maung Shwe, a senior official at the Myanmar Peace Center, told AFP.

Last week, during his first visit to London as part of a European tour aimed at burnishing Myanmar’s international image, Thein Sein said there would be “no prisoners of conscience in Myanmar” by the end of the year.

Rights groups and officials estimate there were between around 100 and 150 political prisoners in Myanmar ahead of Tuesday’s announcement.

Activists welcomed the release, but voiced concern over new arrests in the country.

“Even if we welcome this release, we are very concerned because of the new trials, they continue to send new (political prisoners) to jail,” said Bo Kyi of the Thailand-based Assistance Association for Political Prisoners (Burma), which collects data on imprisoned activists.

He said around 80 convicted dissidents remain behind bars, according to AAPP estimates, with a further 70 people awaiting trial.

One of those released in the amnesty, Brang Shawng, was only arrested last week in a camp for those internally displaced and held on suspicion of involvement with armed ethnic minority fighters from northern Kachin state.

Hla Maung Shwe said around 27 of those being released were rebels from Kachin, where the government is working on brokering a crucial ceasefire deal.

He said some prisoners had already been freed.

A spokesman for U.N. leader Ban Ki-moon said Tuesday: “The Secretary-General welcomes the release of 73 political prisoners in Myanmar and also the recent statement by President Thein Sein that all political prisoners in the country will be released by the end of the year.

“He hopes that these and other measures undertaken recently in the country’s transition to democracy will further strengthen efforts toward a comprehensive nationwide ceasefire and national reconciliation in Myanmar.”

The military junta, which ruled Myanmar with an iron fist for decades, had long denied the existence of political prisoners.

But hundreds of dissidents have been freed since Thein Sein took power two years ago. Last November he announced a review of all “politically concerned” cases.

Campaigners urged the government to go further.

“The president said in Britain that there would be no political prisoners at the end of this year. We would like to say that the promise needs to be implemented precisely,” Myint Aung, a member of the Former Political Prisoners group, told AFP.

He said it was not immediately clear if those freed matched the group’s list of detained dissidents.

“We will continue calling for the release of the rest,” he added.

Thein Sein has been praised by foreign governments for reforms including welcoming democracy champion Aung San Suu Kyi and her opposition political party into parliament.

The quasi-civilian government has also 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.

“Very possibly, over the coming weeks, we will have a nationwide ceasefire and the guns will go silent everywhere in Myanmar for the very first time in over 60 years,” Thein Sein said last week.

Hla Maung Shwe told AFP that the the announcement could lead to “more meetings” with Kachin fighters, indicating that the move may have been part of ceasefire negotiations.

He added that the government’s most senior peace negotiator had personally greeted some rebels after their release.

In response to Myanmar’s changes, the European Union has scrapped most sanctions, except for an arms embargo, and has readmitted Myanmar to its trade preference scheme.

The United States has also lifted most embargoes and foreign companies are now eager to enter the resource-rich nation, with its perceived frontier market of some 60 million potential consumers.