Thousands of Armenians marched through the capital of Yerevan, calling for the resignation of President Serzh Sarkisian.

Witnesses say at least 4,000 people attended Friday's protest by the opposition Armenian National Congress, headed by former President Levon Ter-Petrosyan. The demonstrators also demanded early elections.

The rally is the latest in a series of ANC protests this year.

The ANC has been campaigning for amendments to Armenia's electoral code to take place before any vote. It also wants the release of political prisoners and an investigation into the government crackdown on post-election protests in March 2008 that killed eight people.

The government has rejected the possibility of early elections.

Opposition leaders are planning another rally for next month .

Deadly riots erupted in Yerevan following an election in February, when police clashed with opposition supporters who said the vote was rigged. Official results gave a landslide victory to Mr. Sarkisyan. Mr. Ter-Petrosyan, who disputes the election results, won 21 percent of the vote.

More than 100 opposition members were arrested during post-election violence in 2008, and there have been allegations of police brutality against detainees.