Sannikau's lawyer said late on April 14 that the 58-year-old former deputy foreign minister who subsequently ran afoul of authoritarian President Alyaksandr Lukashenka had received a pardon and returned to the capital.
Supporters got more welcome news hours later, when a democratic activist and former campaign aide to Sannikau who was arrested at the same election-night rally in December 2010 was freed.
Dzmitry Bandarenka was serving a two-year sentence that had been handed down one year ago. RFE/RL's Belarus Service confirmed that, like Sannikau, Bandarenka was released after a presidential pardon.
More Still Imprisoned
The European Union has called for the release of all political prisoners in Belarus -- of whom there are currently around 10 -- and recently stepped up travel and economic sanctions against key Belarusian officials in an effort to put pressure on the Lukashenka government.
The day after his release, Sannikau said he thought the authorities in Minsk were playing a "game" and would be watching closely to see how the international community reacted to the latest releases.
"I think we are witnessing a game," Sannikau said. "I remember the releases of last September -- there was also information that somebody was released but nobody knew who. Now they [the authorities] will watch the reaction to see what will happen after my release or Dima's [Bandarenka's]."
He added: "I think they will release almost all [political prisoners] in the very near future. But we have to stress that until they release all political prisoners, there shouldn’t be any steps on the part of those who are calling for this -- Europe [or] our public opinion."
The OSCE chairperson-in-office, Irish Deputy Prime Minister Eamon Gilmore, expressed relief over the release but stressed concern for other prisoners including another former presidential candidate, Mikola Statkevich.
“This is excellent news for [Sannikau], his family and his friends, but I remain concerned over the fate of other jailed political opponents, notably former presidential candidate [Mikola] Statkevich,” Gilmore was quoted as saying. “I call upon President [Lukashenka] to build upon this positive development and release all remaining jailed opposition leaders."
'Solidarity Saved Me'
Sannikau competed in the controversial 2010 Belarus presidential election, officially finishing second behind Lukashenka in voting that Western watchers say was woefully flawed.
WATCH: RFE/RL’s Belarus Service interviewed Sannikau late on April 14, within hours of his surprise release:
A founder of the Charter 97 group and leading proponent of the European Belarus civil initiative, he was one of many leading opposition figures and sympathizers who remained in jail over charges stemming from the resulting street protests.
"First of all, I'd like to thank the people for their solid support," Sannikau told RFE/RL's Belarus Service after his release. "It was really strong support. I felt it even physically. It was the people's solidarity that not only supported me but saved me."
WATCH the video (in Belarusian) of Sannikau's interview with RFE/RL's Belarus Service after his release
Lawyer Andrei Varvachevitch said late on April 14 that his client "has been pardoned, released from prison, and gone to Minsk."
Sannikau downplayed concerns about his health, saying he was currently suffering from "a cold."
Sannikau was being held at a labor camp in Vitsebsk, in northeastern Belarus, before his release.
He told RFE/RL that he'd been summoned at around 5:30 local time on April 14 by the penal facility's leadership and ordered to collect his belongings.
See RFE/RL Belarus Service's detailed chronicle of how it broke the news of Sannikau's release (in Belarusian)
Bandarenka told RFE/RL's Belarus Service that his release on Orthodox Easter had special meaning for him.
"It is said that everything is in God's hands, and, praise God, today is such a special day," Bandaranka said. "It is a good sign for Belarus. I think that it was a Christian move. Today is such a big holiday that all [political prisoners] should be released today."
Family and friends of other jailed opposition leaders contacted by RFE/RL, including Statkevich, said they had received no indication that any of those jailed individuals were being prepared for release.
Sannikau was among scores of protesters beaten by security forces at postelection protests and was subsequently sentenced to five years in prison on charges of organizing mass disturbances.
Sannikau and his wife, journalist Iryna Khalip, have a young son whom authorities reportedly threatened to take away during the postelection crackdown. He and his son were on hand to greet Bandarenka when he arrived home.
In November, Sannikau was transferred to Vitsebsk from another labor camp, that one in the eastern city of Babruysk.
Khalip, who has complained of frequent harassment by authorities, said in January that Sannikau had been "forced" to author a letter to Lukashenka asking for his freedom.
Sannikau appeared defiant when he was sentenced to five years in prison by a court in May 2011 over his role in stirring public protest over the December 2010 election.
The European Union, the United States, and other international critics have long decried Lukashenka's brutal suppression of dissent.
The 2010 election, which officials said Lukashenka won with nearly 80 percent of the vote, handed Lukashenka a fourth term as president of Belarus.
Seven of Lukashenka's nine challengers in that race have since spent time in jail.