Supporters of Armenian opposition candidate Robert Kocharyan rallied on Friday ahead of snap parliamentary elections this weekend.
Armenian Prime Minister Nikol Pashinyan had called the early polls to end a political crisis after last year's war with Azerbaijan.
The AFP news agency estimated some 20,000 supporters of Pashinyan's main rival, Kocharyan, gathered at a central square in the capital, Yerevan, on Friday evening.
According to a poll released Friday by MPG, a polling group affiliated with Gallup International, 28.7% of voters favored Kocharyan's Armenia Alliance and 25.2% for Pashinyan's Civil Contract party.
Kocharyan is a native of the Nagorno-Karabakh region, which was the center of the conflict with Azerbaijan.
He was accused of acting unlawfully for imposing a state of emergency after a disputed election at the end of his term as president of Armenia from 1998 to 2008. The clashes that followed between police and protesters left at least 10 dead.
Pashinyan has been under pressure since ethnic Armenian forces lost a six-week war against Azerbaijan and ceded territory in and around the Nagorno-Karabakh region.
Kocharyan pledged to start negotiations on Nagorno-Karabakh's borders if he came to power.
Whoever forms a majority in parliament can elect the prime minister, who the president nominates.
How did Armenia's political crisis unfold?
Protesters have called on Pashinyan to step down over the terms of a Russian-brokered peace deal that ended the conflict with Azerbaijan.
Pashinyan himself had called the deal a disaster but said he had to sign it to prevent further human and territorial losses.
The prime minister tried to dismiss the military's chief of staff Onik Gasparyan, claiming that there had been an attempted coup, after the military joined calls for Pashinyan to step down.
Gasparyan refused to leave, and the country's president, Armen Sarkisian, also called for Pashinyan to go.
fb/sms (AFP, Reuters)