A lawyer for Burma's main opposition party says the Burmese government has freed six political prisoners from the notorious Insein Prison.

The lawyer, Aung Thein, says the prisoner release took place shortly after a U.N. human rights envoy, Paulo Sergio Pinheiro, met with political detainees at the prison Thursday.

Aung says five of the prisoners freed were members of the opposition National League for Democracy, and the sixth was a student activist named Thet Naung Soe.

Pinheiro's visit to the Insein Prison marked the end of his first visit to Burma in four years. He was in the country to investigate how many people were killed or jailed during a crackdown by Burma's military government on pro-democracy protests in September.

Pinheiro said he met with several prisoners, including labor activist Su Su Nway, who was arrested this week, and the longest serving political prisoner in Burma, journalist Win Tin.

The envoy said his request to meet detained opposition leader Aung San Suu Kyi, who is under house arrest, had been refused.

Burmese officials say 10 people were killed and nearly 3,000 detained in the September crackdown. Diplomats and human rights groups say the true figures are much higher.

Some information for this report was provided by AFP and Reuters.