Burma has begun releasing some prominent political prisoners as part of a government amnesty program, in the latest move toward political reform by the country's military-backed government.

Burmese state media said that 651 detainees were being freed under a presidential pardon in order to take part in “nation-building.”

Family members said prominent democracy activist Min Ko Naing was among those released. Min was a key student leader in the 1988 pro-democracy uprising that was brutally suppressed by the country's former military junta. Some reports also suggest the amnesty may include Shin Gambira – a Buddhist monk who led street protests in 2007.

The United States and European Union say they will not end economic sanctions until Burma's new, nominally civilian government frees all of its political prisoners.

President Thein Sein released about 230 political detainees in October. But around 1,000 political prisoners are thought to still be in Burmese prisons.

Friday's prisoner release comes a day after the Burmese government signed a cease-fire deal with the ethnic Karen rebel group, in an apparent move toward ending one of the world's longest-running insurgencies.

The agreement marks the first declared break in fighting between the government and the rebel force since just after the country gained independence from Britain in 1948.

Meanwhile, a leading congressional voice behind U.S. sanctions on Burma, Senator Mitch McConnell, says he will begin a three-day visit to the country on Sunday to assess political reforms. He plans to meet pro-democracy activist Aung San Suu Kyi and government officials in his first ever trip to Burma.

Another U.S. congressman, Representative Joe Crowley, is currently in Burma to encourage the government's reform efforts.

After landmark visit to Burma in November, U.S. Secretary of State Hillary Clinton suggested that Washington would consider lifting its sanctions against Burma's new government if it continues reforms.