Sarksyan, a close ally of Russian President Vladimir Putin, had served as Armenia's president for a decade until this month and had faced accusations of clinging to power when parliament elected him as prime minister last week.
"The movement on the streets is against my office". At that meeting held in the presence of journalists, Sarkisian rejected Pashinian's demands for his resignation.
The Armenian government quickly named former Prime Minister Karen Karapetian as acting premier.
On Sunday police had detained three opposition leaders and almost 200 protesters, drawing a rebuke from the European Union.
The whereabouts of Pashinyan, the leader of the Civil Contract Party, were unclear after he was detained.
Politicians and media in Azerbaijan have come out in support of the protests in Yerevan, but their messages seem off-target as seen from an Armenian perspective, Eurasianet's Joshus Kucera wrote Saturday.
"[Opposition leader] Nikol Pashinian was right", he said in a written address to the nation.
"I am leaving the post of prime minister", he said. I was mistaken. There are several solutions to this situation, but I will not apply to any of them.
Stephen Curry brilliantly celebrates Klay Thompson three-pointer before it goes in
San Antonio might have been able to steal game 2 in Oracle Arena Monday night, but they had a historically bad shooting night. In opposition of Golden State, games involving the Spurs have a slight tendency to finish under the O/U total (51.2 percent).
Sargsyan maintained close ties as president with Russian Federation, which has a key military base in Armenia and sells arms to the Caucasus republic that's locked in a decades-long conflict with neighboring Azerbaijan over the disputed territory of Nagorno-Karabakh.
"I think his resignation is a clear demonstration of a democracy in force".
The protest leader was arrested later in the day.
A group of serving soldiers joined the protests while the country's defence ministry threatened to take "serious measures" against them.
Mr Pashinyan congratulated the people on their "victory" following the resignation.
"You have won, the proud citizens of Armenia!"
"Dear compatriots, I am addressing you for the last time as the head of the state". The demonstrations, led by opposition, have gared tens of thousands of people throughout day to demand that Sargsyan not continue in power as Prime minister after having left presidency of country less than a week ago. "We need to tell society about this", Vigen Sarkisian said.
Peskov dismissed a question on whether Russian Federation would interfere in the crisis, which he called "exclusively an internal affair", as "absolutely inappropriate". In the wake of the announcement, people in Yerevan, the capital, waved flags and cheered.