Armenian police have arrested 30 opposition activists accused of causing clashes with police which led to a state of emergency.
A state of emergency has been imposed in Yerevan
The figure was released by the Armenian prosecutor-general, referring to Saturday's riots in the capital Yerevan, in which eight people died.
The opposition accuses the authorities of having rigged last month's presidential election.
Separately, Armenian and Azeri troops are reported to have exchanged fire.
The clash happened on Tuesday in the Mardakert area of northwestern Nagorno-Karabakh, a disputed Armenian-controlled enclave inside Azerbaijan, Itar-Tass news agency reported.
An Azeri TV station, ANS, said three Azeri troops had been killed, but that figure has not been confirmed by other sources.
Armenia's Foreign Minister, Vartan Oskanian, was quoted as saying there had been Armenian casualties. A ceasefire was agreed in 1994, after Armenia had taken control of the territory in a full-scale war.
In Yerevan, troops are enforcing a state of emergency and 30 people are under arrest "for using violence, causing danger for the life and health of police," the prosecutor-general said.
The election was officially won by PM Serzh Sarkisian, who beat opposition candidate Levon Ter-Petrosian.
Official results gave Mr Sarkisian 53% of the vote in the 19 February election, with Mr Ter-Petrosian on 21.5%.
International observers judged the election to be generally democratic but noted some problems with the vote count.
Mr Ter-Petrosian vowed to continue the protests
Two pan-European bodies, the Council of Europe and the Organisation for Security and Co-operation in Europe (OSCE), have voiced concern about the situation in the former Soviet republic.
Armenia's constitutional court has now started considering the opposition's challenge to the election results - although government ministers have told their opponents to accept defeat.
Earlier this week, Mr Ter-Petrosian, a former president, vowed to continue protesting against the result of the poll, saying it was rigged. He warned that there could be years of political conflict ahead.
He expressed regret about the eight people who died on Saturday. But he blamed the government for the pitched battles between police and protesters, who had set up barricades in the city centre.
The authorities said they had to restore order after 11 days of mass demonstrations which they had repeatedly warned were illegal.
Outgoing President Robert Kocharian declared a state of emergency was in force until 20 March.