Mongolia's opposition Democratic Coalition appears to have made strong gains in Sunday's general election.
Turnout was almost 80%
Early results suggested the democrats and ruling MPRP could end up with more than 30 seats each in the Great Hural, or parliament.
The MPRP held all but four seats in the outgoing parliament, but its failure to tackle rising poverty appears to have lost it support.
The party which wins most seats gets to nominate the country's prime minister.
Early official results gave the MPRP and the democrats 36 seats each.
Election officials were still counting votes in some districts late on Monday, amid complaints of irregularities from both sides.
Final results are expected on Tuesday.
Prime Minister Nambaryn Enkhbayar accused the opposition of cheating.
"I have a lot of information on embezzlement.. some candidates bought the votes," he said at a press conference on Monday.
He alleged that the opposition offered money and bottles of vodka to sway voters.
"We must put an end to the fraud. The result is simply impossible," he said.
Voter turnout was reported to be 77%, as people travelled by horse, camel and four-wheel drive vehicles to reach polling stations on Sunday.
The once-communist MPRP had dominated the campaign, and the unofficial results - if confirmed - would constitute a big shift in popular mood.
But the BBC's Francis Markus says Mongolian politics can be full of surprises, like the MPRP's own shock victory four years ago.
The Democrat Coalition then won 46% of the vote but, under the country's first-past-the-post system, narrowly lost almost all the country's constituency races.
This time around, the democrats tried to make a virtue of their lack of campaign funds.
They were also hoping to gain from a wariness of a return to one-party rule.
That is despite the MPRP's reforms after decades of Soviet-style policies, our correspondent says.
The economy overshadowed the elections.
Mongolia appears to be enjoying relatively healthy growth, with its mining and infrastructure sectors attracting keen interest from commodity-hungry China.
But as the country still grapples with the legacy of the Soviet Union's collapse, growing numbers of Mongolians remain trapped below the poverty line.