Aram Bareghamian, who headed a regional branch of a major political party aligned with the main opposition Armenian National Congress (HAK), was freed one month after a prison near the central town of Sevan recommended his early release.
The recommendation was seconded later in April by a state commission dealing with parole applications.
Bareghamian was among more than 100 loyalists of HAK leader Levon Ter-Petrossian who were arrested in the wake of the March 2008 unrest in Yerevan. He was sentenced to six years in prison for allegedly assaulting a police officer.
The prison sentence was based on the policeman's testimony. Both Bareghamian and the HAK leadership consider the case politically motivated.
"Even the prison inmates recognized me as a political prisoner," Bareghamian told RFE/RL after the court announced its decision on May 2. "I was brought here by illegitimate authorities because of my political views."
He said he would now strive for his acquittal through other courts and seek the punishment of police who, he said, gave "false testimony" against him. He also pledged to continue to fight for "regime change."
Bareghamian's release reduced to five the number of opposition activists jailed in connection with the controversial 2008 election. President Serzh Sarkisian indicated last week that they will all be freed soon as part of his overtures to the Ter-Petrossian-led opposition.
The HAK leader stressed the importance of this and other government concessions as he addressed thousands of supporters at a rally in downtown Yerevan on April 28.
He said the HAK was ready to start a dialogue with the Armenian authorities, instead of seeking another "physical confrontation" with them.
Ter-Petrossian predicted that all "political prisoners" would be set free by May 28, the anniversary of Armenia's independence in 1918.
On April 29, parliament speaker Hovik Abrahamian and other leaders of the pro-government majority in parliament asked Sarkisian to consider pardoning Sasun Mikaelian, one of the most prominent opposition activists remaining in jail and, like Sarkisian, a veteran of the Nagorno-Karabakh war.
"His health condition is such that it allows for his early release," Galust Sahakian, the parliamentary leader of Sarkisian's Republican Party of Armenia (HHK), told RFE/RL over the weekend. "I think the president will respond to our appeal."
Presidential press secretary Armen Arzumanian told RFE/RL the response would come "in due course." He refused further comment.
Ter-Petrossian spokesman Arman Musinian also declined to comment.