Incumbent Serzh Sargsyan looks set to win Armenia's presidential election with 61.4 percent of the vote, according
to official partial results, with his main rival contesting the result.
The Central Election Commission said early tallies from more than 50 percent of the voting precincts showed former foreign minister Raffi Hovannisian in second place with 33.9 percent.
Hovannisian swiftly insisted he was the real winner and called on Sargsyan to concede defeat.
Eduard Sharmazanov, the deputy parliament speaker who is also the spokesman of Sargsyan's ruling Republican Party, rejected allegations of fraud.
"These elections were the best in the history of independent Armenia," he said. "The exit poll results show that Serzh Sargsyan was the only favourite."
Former prime minister Hrant Bagratian was on course for three percent as was the Soviet-era dissident Paruyr Hayrikyan, exit polls said.
The vote was marked with the absence of strong opposition to the incumbent leader and shadowed by last month's mysterious assassination attempt against Hayrikyan which at one point risked derailing the holding of the ballot.
The authorities were hoping for a peaceful process that will improve the country's chances of European integration, after the vote that brought Sargsyan to power in 2008 ended in clashes in which 10 people died.
Hovannisian said the election marked "the most crucial day in our country's modern history" but denounced irregularities in voters' lists and voting procedures.
"These were shameful elections with a huge number of violations. The results of the exit poll do not show reality but what the authorities wanted."
- Hovsep Khurshudian,
His campaign alleged a range of violations, ranging from the use of "vanishing ink" to allow multiple voting and "caravans" of taxis and buses to take pro-government voters to the polls.
"These were shameful elections with a huge number of violations. The results of the exit poll do not show reality but what the authorities wanted," Hovannisian's spokesman Hovsep Khurshudian told AFP news agency.
He vowed that Hovannisian's supporters would hold a protest meeting on Tuesday evening.
The police dismissed the allegations of violations as "obvious fiction."
Turnout was 60.1 percent, the Central Elections Commission said.
Sargsyan, 59, is a veteran of the 1990s war with Azerbaijan over the disputed region of Nagorny Karabakh and derives much of his popularity from a tough militaristic image.
Hovannisian, 54, was born in the United States and used to practise law in Los Angeles before moving to Armenia following its devastating earthquake of December 1988.
"I voted for Serzh [Sargsyan]. He can lead the army and take important decisions at the right moment," carpenter Vazgen Akobyan told AFP at a polling station in Yerevan.
"I support Raffi Hovannisian. He has a Western mentality, he is intelligent, he promised to fight corruption and create new jobs," said another voter, unemployed Siranush Mnatsmkanyan.
The World Bank estimates that 36 percent of Armenians live below the poverty line. Economic hardship and unemployment have driven nearly a million Armenians out of the country over the past two decades.
But campaigning has also focused on Armenia's long-running disputes with arch-foe neighbours Turkey and Azerbaijan.
No final peace deal has been reached with Azerbaijan over the Armenian-controlled Azerbaijani region of Nagorny Karabakh as the risk of a new conflict remains palpable.
International observers from the Organisation for Security and Cooperation in Europe have monitored voting and are scheduled to give their verdict at a news conference on Tuesday.