International observers monitoring elections in Azerbaijan say the vote did not meet democratic standards.
Observers reported widespread irregularities in vote-counting
The Organization for Security and Co-operation in Europe complained of significant irregularities in the parliamentary vote and vote-counting.
With nearly all votes counted, the ruling New Azerbaijan Party had won 63 of the 125 seats, Azeri officials said.
The main opposition Azadlyq bloc, which is planning street protests against the results, got five seats.
The elections on Sunday were the first since President Ilham Aliyev replaced his father, Heydar Aliyev, in 2003.
Council of Europe observers said the count in 43% of polling stations had been "bad or very bad".
The BBC's Natalia Antelava, in the capital Baku, says the parliamentary vote was seen as a test of democracy in the oil-rich former Soviet republic - a test it has failed.
She says the OSCE verdict gives the opposition more leverage and more reason to challenge the result in court and in the streets.
The opposition bloc, who chose orange as their campaign colour in imitation of Ukraine's "Orange Revolution", is planning street protests.
Ali Kerimli, a joint leader of the Azadlyq bloc, said a peaceful protest would start on Tuesday.
"It will be the start of continual protests until the election is overturned," he told Reuters.
Azadlyq called for the results to be annulled in four-fifths of the electoral districts.
The Central Election Commission insisted the vote had been democratic and dismissed the allegations of fraud.
The OSCE said there had been some improvements before election day, but shortcomings included "interference of local authorities, disproportionate use of force to thwart rallies, arbitrary detentions, restrictive interpretations of campaign provisions".
"The shortcomings that were observed, particularly during election day, have led us to conclude that the elections did not meet Azerbaijan's international commitments on elections," said Alcee Hastings, President of the OSCE Parliamentary Assembly and the Special Co-ordinator for the short-term observers.
"It pains me to report that progress noted in the pre-election period was undermined by significant deficiencies in the count."
Hundreds of international observers monitored the poll, and the US government sponsored one exit poll as a check on the official count.
Washington has a strong interest in stability in the Caspian Sea nation, which sits at a strategically vital point between Iran, Russia and Turkey.
The government has said it will act to prevent a Ukraine-style revolution - the street protests which swept liberal leader Viktor Yushchenko into power after disputed elections.