By Hasmik Mkrtchyan
YEREVAN (Reuters) - A leading opposition group in Armenia said on Tuesday a parliamentary election won by the president's party had been marred by fraud, and vowed to ask a top court to overturn the results.
Two days after Sunday's election in the former Soviet Republic, about 5,000 supporters of former president Levon Ter-Petrosyan's Armenian National Congress took to the streets in central Yerevan.
The Republican Party of President Serzh Sarksyan won about 68 seats, a majority in the 131-seat parliament, according to results released on Monday.
The Armenian National Congress won seven seats, but its leaders argue the election should be thrown out altogether, saying widespread vote-buying and other violations had taken place.
"We took a decision to appeal to the Constitutional Court to annul the results of the election," said Aram Manukyan, a leader of the congress.
"Each election is worse than the last," Ter-Petrosyan said.
International monitors have given a mixed assessment of the vote in Russia's main ally in the strategic South Caucasus. They praised Armenia for electoral reforms and a peaceful vote but criticized what they said were violations of the campaign law and interference by parties.
Republican Party officials said the election was democratic.
Voting irregularities marred Armenia's 2007 parliamentary election, while clashes between police and protesters led by Ter-Petrosyan killed 10 people after the 2008 presidential vote in which Sarksyan was elected.
The Armenian National Congress, which had no seats in the previous parliament, said, however, that it would not refuse the parliament seats it had won.
"The bloc's participation in the work of parliament will give new impulse to our struggle," said another congress leader, Stepan Demirchyan.
Armenia, a landlocked nation of 3.3 million, hosts a Russian military base and is locked in hostile relations with neighboring Azerbaijan nearly two decades after a war over the disputed territory of Nagorno-Karabakh.
The South Caucasus lies between Russia, Turkey, Iran and Central Asia and is emerging as an important route for oil and gas exports from the Caspian Sea to world markets, although Armenia has no pipelines of its own.
(Writing by Steve Gutterman; Editing by Alessandra Rizzo)