The freeing of prisoners by the outgoing administration of President Thein Sein comes after US Assistant Secretary of State Antony Blinken urged Myanmar to free all political prisoners during a visit on Monday.
The amnesty boosts the legacy of Thein Sein, whose semi-civilian government in 2011 replaced a junta that had run Myanmar for 49 years, ushering in a series of political and economic reforms. It deprives the incoming government of Suu Kyi, who had been likely to push for a quick prisoner release, of an easy political win.
"So far, 18 political prisoners were released from Insein Prison. They will release a total of 21 people today," a prison official told Reuters.
Insein is one of Myanmar's largest prisons. It is used for jailing political prisoners, including Suu Kyi for s stint in 2003, along with criminals, and is notorious for its poor conditions and bad treatment of inmates.
"I hope the new government will bring solutions for the problems that the previous government created for the people," said Htay Aung, 48, released on Friday from Insein. He spent nine months in jail for taking part in several protests.
Phillip Blackwood, a New Zealand citizen jailed in March for two and a half years for insulting religion, was also likely to be released on Friday. He had used a psychedelic image of Buddha wearing headphones to promote a party at a Yangon bar.
Blackwood, the highest-profile foreign political prisoner held in Myanmar, has also been held at Insein. It was unclear if two Myanmar citizens jailed along with Blackwood would be released.
Zaw Htay, a director at the president's office, said on his Facebook page that 102 prisoners would be freed. He said also that 77 death sentences would be reduced to life imprisonments.
"Most of them were arrested for staging protests. As far as I know, there will be 101 political prisoners who will be released in the coming days," said Bo Kyi, Joint Secretary of political prisoner watchdog the Assistance Association for Political Prisoners (AAPP).
Myanmar's incarceration of more than 2,000 journalists, activists, politicians and even comedians during decades of military rule was a key factor behind Western sanctions.
Hundreds were released by Thein Sein's government, but human rights groups had complained that many were still in jail. In December, there were 129 political prisoners incarcerated in Myanmar and 408 activists were awaiting trial for political actions, according to AAPP's website.
"A full amnesty could be the president's swan song and send the right signals to the new government that locking people up for peaceful dissent is not democratic progress," said Dave Mathieson, senior researcher on Myanmar at Human Rights Watch.
A new parliament dominated by Nobel peace laureate Suu Kyi's National League for Democracy will sit for the first time on Februrary 1.