Police detained 77 people following clashes when thousands of protesters converged on center of the capital Yerevan and surrounded the heavily guarded government building.
Pashinyan and other cabinet members were able to get into the building despite the unrest.
“Now our goal is that they don’t get out until Nikol Pashinyan resigns,” Ishkhan Saghatelyan, a leading member of the opposition Dashnaktsutyun party, was quoted as saying by the Russian state Tass news agency.
Nagorno-Karabakh lies within Azerbaijan but was under the control of ethnic Armenian forces backed by Armenia since a separatist war there ended in 1994. That war left Nagorno-Karabakh itself and substantial surrounding territory in Armenian hands.
Heavy fighting erupted in late September in the biggest escalation of the decades-old conflict between Armenia and Azerbaijan, killing more than 5,600 people on both sides.
The Russian-brokered peace agreement stipulated that Armenia hand over control of some areas it holds outside Nagorno-Karabakh’s borders. Azerbaijan also retained control over areas of Nagorno-Karabakh it had taken during the conflict.
The peace deal was celebrated in Azerbaijan as a major triumph, but sparked outrage and mass protests in Armenia where thousands repeatedly took to the streets. Pashinyan has defended the deal as a painful but necessary move that prevented Azerbaijan from overrunning the entire Nagorno-Karabakh region.
Associated Press writer Daria Litvinova in Moscow contributed to this report.
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