Armenian police detained 88 people at a protest in the capital Yerevan by demonstrators demanding the resignation of Prime Minister Nikol Pashinyan over his decision to cede several border villages to Azerbaijan.
Armenia said last month it would return the uninhabited villages in what both sides said was an important milestone as they edge towards a peace deal after fighting two wars since the collapse of the Soviet Union.
The decision has angered many in Armenia. Protesters led by a senior Armenian cleric reached Yerevan on Thursday after walking for several days from a village in the country's northeast, a distance of some 100 miles (160 km).
Archbishop Bagrat Galstanyan called for Prime Minister Pashinyan's resignation at rally of thousands of supporters, who he encouraged to begin acts of civil disobedience aimed at toppling the government.
Opposition parties in Armenia's parliament have said they will try to begin impeachment proceedings against Pashinyan, whose Civil Contract party retains a majority of lawmakers, and is unlikely to break with him.
Armenia is a treaty ally of Russia and traditionally Moscow's closest partner in the South Caucasus, but bilateral relations have sharply deteriorated in recent months as Yerevan has sought to build ties with the West, blaming Russia for failing to defend it from Azerbaijan.