Armenian security forces moved to clear opposition demonstrators from the centre of the capital, Yerevan, after 11 days of protests.
Violence erupted on the streets with reports of security forces firing live rounds into the air as protesters hurled petrol bombs and stones.
The city has seen thousands of opposition supporters marching or manning a tent protest in the centre.
Protesters accuse Prime Minister Serzh Sarkisian of stealing the vote from their candidate, Levon Ter-Petrosian, though foreign observers say the vote was generally democratic.
Mr Ter-Petrosian said that a revolution was under way against the government.
Mr Sarkisian, whose portrait is here being kissed by a supporter, officially won 52.9% of the vote to Mr Ter-Petrosian's 21.5% on 19 February.