Thousands of supporters of Levon Ter-Petrosian, Armenia's former president, rallied for 11 days to denounce the victory of Serzh Sarkisian in last February's presidential election, before street battles broke out with riot police.
Ter-Petrosian finished second in the vote and authorities accused the opposition of trying to overthrow the government.
Two police officers and eight civilians were killed in the clashes and dozens more were injured, many from gunshot wounds.
Western election monitors said the vote was broadly in line with the country's international commitments, but that further improvements were necessary.
More than 50 people received jail sentences over the unrest.
A number have since been pardoned by Sarkisian, going some way to placating European human rights bodies.
Human Rights Watch said Armenia's public prosecutor should step up efforts to conduct an independent, impartial investigation into the events.
It urged the country to address shortcomings in the electoral process and pervasive public distrust that have left Armenia "stuck in a cycle of uneven contests, fraud, and disputes that more often than not spill onto the streets".
"To the extent that it exists, real political competition is volatile with a permanent risk of violence," the report said.
Armenia has seen repeated political violence and post-election protests since gaining independence with the Soviet Union's collapse in 1991.