Armenian President Robert Kocharyan has narrowly failed to garner enough votes to win Wednesday's election outright, election officials have announced.
The announcement followed opposition protests
Voting in the presidential poll will have to go to a second round after Mr Kocharyan apparently received 49.8% of ballots.
The announcement came after protests by thousands of opposition supporters in the capital Yerevan when early results suggested 49-year-old Mr Kocharyan would avoid a run-off vote.
Opposition candidates said they would refuse to recognise the result, alleging widespread fraud.
Riot police formed a chain around the election commission building to prevent the protesters from entering.
The latest result means that Mr Kocharyan, will face his strongest challenger, Stepan Demirchyan, in a second round scheduled for 5 March.
He is the son of former parliament speaker Karen Demirchyan - one of eight people killed in a 1999 parliamentary massacre.
Mr Demirchyan won 27.7% of the vote on an anti-corruption platform, capitalising on the popularity of his father, a Soviet-era Communist party boss who lost to Mr Kocharyan in the 1998 election.
International observers from the Organisation for Security and Co-operation in Europe (OSCE) and the Parliamentary Assembly of the Council of Europe (PACE) said Wednesday's election was marred by significant irregularities.
Peter Eicher, who head the OSCE's 200-strong team from 35 countries, also spoke of a pre-election period marred by intimidation, and manipulation including a serious incident of violence in which an opposition campaign manager was stabbed.
However, a team of observers from former Soviet republics described the elections as free, transparent and democratic.
No foregone conclusion
Mr Kocharyan is credited with bringing a measure of stability to the country.
Electricity and natural gas supplies have been widely restored under his presidency, and pensions have begun to be paid on time.
Poverty, however, is widespread, with average monthly salaries of about $40.
Correspondents say the second round could be close, as he will face a single opposition candidate, rather than the eight who stood on Wednesday.