Armenian opposition leader Nikol Pashinyan has been released by police following his detention over the weekend.
A live-stream from the capital Yerevan showed Pashinyan being set free, Reuters reported. He had been arrested yesterday joining two other opposition leaders and more than two hundred protesters rounded up by the authorities.
Demonstrators are demanding that newly Serzh Sarksyan, who served the maximum two terms as the country's president, step down from his new role as prime minister.
Pashinyan's arrest had come after televised talks with Sargsyan collapsed, with the prime minister walking out.
Protests in Yerevan continued this morning, with uniformed soldiers joining the rallies for the first time. The defence ministry said it would take action against any troops found to have taken part.
Critics accuse Sarksyan of ruling the South Caucasus nation of around 3 million people for too long, of being too close to Russia which has military bases inside Armenia, and of doing too little to root out corruption.
Sarksyan says his country needs him and that his party enjoys large-scale popular support.
Under a revised constitution approved in a 2015 referendum, most state powers shifted to the prime minister while the presidency has become a largely ceremonial post.
Armenia is facing its biggest political crisis in a decade . The protests threaten to destabilise a key Russian ally in a volatile region as "people power" takes to the streets.