Addressing the turmoil taking place on the streets, he said that if people were truly in protest, there would be millions of people in the streets, not just thousands, "you know full well how many people are taking part in these demonstrations".
Yesterday, Pashinyan announced a start of a "Velvet Revolution" and urged protesters to block governmental buildings.
More than 16,000 people rallied in Armenia's capital on Wednesday to protest the election of former president Serzh Sarkisian as prime minister, viewed by the opposition as a power grab.
"We have a revolutionary situation in Armenia". He also called for spreading protests across Armenia.
Before he was officially sworn in, Mr Sargsyan told parliament that under the new constitution the prime minister would be "under parliament's control and can be replaced for political reasons".
Justifying his desire to continue leading the after 10 years as president, Sarkisian said that even if he were not elected as prime minister, his input would be such that he would be "running the country from behind the scenes".
Constitutional amendments approved in 2015 have transferred governing powers from the presidency to the premier.
Russian President Vladimir Putin called Sarkisian late Tuesday to congratulate him on his election, the Kremlin spokesman said.
Demonstrations in Gyumri are held near the Regional Administration office of Shirak.
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On April 17, parliament voted 76-17 with no abstentions to make Sarkisian prime minister.
Earlier, the press Secretary of the Armenian police Ashot Aharonyan said that several protesters taken to police stations.
"But the opposition lacks political resources to force Serzh Sarkisian to resign".
"The chances of the ongoing protests growing into a revolution are low, but in case the authorities fail to deliver on the people's main demand - the demand for change - a revolution will not take long to arrive", he added.
On Monday police used stun grenades against protesters who tried to break through a barbed wire cordon to get to the parliament building.
President Armen Sarkisian, who is not related to Serzh Sarkisian, issued a statement the same day warning against disturbances.
Member of Council of Yerevan and the president of "Yerkir Tsirani" party, Zaruhi Postanjyan initiated protests in the streets of Vanadzor encouraging everyone to join the request of Serzh Sargsyan quitting his new post as PM.
In 2014 Mr Sarkisian promised that he would did intend becoming prime minister if Armenia switched from a presidential to the parliamentary system.
Sargsyan served as Armenia's president from 2008 until stepping down because of term limits.