The demonstrators have gathered outside the Matenadaran library of ancient manuscripts in the capital center, despite initially being denied permission to gather by city authorities. Police on June 19 warned protesters to stay away from the center, saying they had permission to rally only at a location on the outskirts of Yerevan.
Thousands of protesters are assembled at Matenadaran, one of the city's most prominent sites for public gatherings. Protest organizers said as many as 50,000 people were gathered; police put "maximum" turnout at 10,000.
Early in the day, police had set up checkpoints in an attempt to prevent traffic from reaching the site. But Aleksandr Afyan, the deputy police chief in Yerevan, told RFE/RL's Armenian Service the checkpoints were eventually removed in order to free up traffic jams and after police officials received assurances from opposition leaders that the protest would be peaceful.
Levon Zurabyan of the National Movement opposition group told assembled protesters that organizers had agreed to cooperate with the police, and called on participants to help maintain a controversy-free gathering. Opposition leader and former President Levon Ter-Petrossian is among the speakers due to address the crowd.
The gathering is the first of its kind since 10 people were killed during or as a result of violent clashes between police and protesters in March. The fatalities followed days of protests against the conduct of the country's February 19 presidential election, in which then-Prime Minister Serzh Sarkisian -- the handpicked successor of the outgoing president, Robert Kocharian -- claimed victory with an official result of 53 percent of the vote.
Ter-Petrossian, his main opponent in the contest, disputed the results, saying he was the rightful winner and alleging the election was marred by numerous voting irregularities.
International observers from the Organization for Security and Cooperation in Europe and the Council of Europe were critical of the vote, noting the lack of a "level playing field" during the election campaign.
The Council of Europe's Parliamentary Assembly (PACE) is due to hold an urgent debate on Armenia during its June 23-27 summer session to assess Yerevan's compliance with more than a dozen demands leveled by the assembly following the postelection violence.
The demands, spelled out in Resolution 1609, which was adopted by PACE in mid-April, called on Armenian authorities to hold an independent and transparent inquiry into the events of March 1, urged the release of political opponents jailed in the days following the elections, and demanded dialogue between the government and the opposition.
The PACE Monitoring Committee announced on June 20 that Armenia's progress in meeting the demands was "insufficient." PACE had earlier warned it would consider suspending the voting rights of Armenia's delegation to the summer session if progress on Resolution 1609 had not been made.RFE/RL's Armenian Service contributed to this report