The rally followed daylong pickets and marches around the capital on 18 April, with police detaining dozens of demonstrators as they tried to block streets and interrupt traffic.
Addressing the rally on Republic Square, opposition leader Nikol Pashinian urged people across Armenia to put pressure on local authorities to make statements in support of the protest movement, saying it would help achieve a change of government.
The opposition leader also called for sit-ins inside administrative buildings and government offices across the country "so that even Serzh Sarkisian himself has no place to sit," and reiterated his call on demonstrators to remain peaceful.
Pashinian later called on the protesters to gather in front of the government offices on Republic Square at 8 a.m. local time on 19 April, to try to prevent ministers from attending Sarkisian's first cabinet meeting.
Earlier in the day, Pashinian led a crowd of hundreds to Sarkisian's office on Marshal Bagramian Avenue, a main thoroughfare near parliament, after pledging to expand daily "blockades" of key government buildings.
Police deployed in force in nearby France Square, where they detained a number of protesters and restored traffic. Riot police with shields stood along the street adjacent to the square to ensure uninterrupted traffic.
In front of government offices, demonstrators called on civil servants to take part in the protest movement "for our future, freedom, and homeland."
According to Armenian Police, 66 protesters have been detained so far.
