Aung Thein says the senior leader of the ethnic Karen National Union rebel group, Mahn Nyein Maung, was released Monday from Yangon’s Insein prison.
He was arrested last year by Chinese authorities, who deported him to Burma, where he was sentenced last week to 20 years in jail.
The government did not explain the pardon. Aung Thein says it is likely aimed at helping ongoing peace talks with Karen insurgents.
The military-backed but elected government is seeking cease-fires with ethnic rebel groups as part of political reforms started last year after decades of repression under military rule.