Several thousand people are protesting in the Armenian capital against a hike in electricity prices.
About 5,000 demonstrators marched Monday to the presidential headquarters, but were stopped by phalanxes of riot police backed by water cannons.
The protesters then sat on the road, blocking traffic. Police warned they would disperse the rally.
The demonstrators are demanding that the government reconsider its decision to increase electricity prices for households by 17-22 percent.
The landlocked country's economy is hobbled by the longstanding closure of its borders with Azerbaijan and Turkey over the conflict in Nagorno-Karabakh.