Defeated ex-premier Khaleda Zia dismissed the result of Bangladesh's general election as unacceptable on Wednesday, saying the poll won by a landslide by her bitterest rival had been stage-managed.
In a brief address on national television just after midnight, Zia said her party had evidence of rampant vote-rigging and that the high figures given by the Election Commission for voter turnout were false.
Her rejection threatens to throw the impoverished south Asian nation into fresh political uncertainty after two years of rule by an interim army-backed government.
"I thank the chief election commissioner for implementing a stage-managed election. This election is not acceptable to the BNP," Zia said, referring to her Bangladesh Nationalist Party.
"It also won't be acceptable to the people," she warned.
The BNP won just 27 of the possible 300 seats in Monday's election and its main ally, the Islamist party Jamaat-e-Islami which held 17 seats in the last elected government, picked up just two.
The Awami League of Sheikh Hasina Wajed -- another former prime minister -- won 231 seats.
Official results of two seats have not been released, while another will be contested next month after the death of a candidate.
The private online newspaper bdnews24.com said that Zia and her party were now considering what legal steps to take.
Zia's BNP had won the last election in 2001 by a huge margin, but Election Commission spokesman SM Asaduzzaman said Sheikh Hasina had won convincingly this time.
"She has a clear majority to govern without any other party," he told AFP.
The election attracted a record turnout of 85 per cent, the commission said, a figure which reached 90 per cent in rural areas.
Election Commissioner Shakhawat Hossain told AFP that although no date had been set, the new government was likely to be sworn in early next month.
"The maximum timeframe is one month but the signal that we are getting from the outgoing government is that power will be transferred by January 7."
Sheikh Hasina and Zia, known as the battling begums for their rivalry, had ruled Bangladesh alternately from 1991 until the caretaker administration was installed two years ago following rampant political violence.
Their feud has been blamed for paralysing politics, and the interim regime made efforts to shake up the system.
A UN-funded digital electoral roll eliminated 12.7 million fake names and appeared to have put a lid on the kind of widespread vote-rigging decried in previous polls, observers said.
Both women were also detained in custody for corruption, but the government agreed to release them to contest the vote.
A team of South Asian poll monitors concluded voting had been "free, fair and transparent," while European Union observers said that an early assessment showed procedures had been correctly followed.
The EU observers were to release a full report later Wednesday and reports from other overseas monitors, including the Commonwealth, were also expected during the day.
"All Bangladeshis can take great pride in the success of these elections," the US State Department said in a statement.
"The high voter turnout underscores the people's desire to see democracy restored as well to have a voice in their future."
Around 50,000 troops had been on alert nationwide during Monday's voting, while 600,000 police officers were deployed to crack down on fraud or prevent disruption at the 35,000 polling booths.
A ban on political rallies ends midnight on Wednesday.
Sheikh Hasina, 61, who has not yet spoken in public since her victory, is the daughter of Mujibur Rahman, who led Bangladesh in its liberation struggle against Pakistan in 1971 and was assassinated in a 1975 military coup.
A press conference scheduled for Tuesday was cancelled because of security fears, her spokesman said.
She herself was targeted by Islamic extremists in 2004, narrowly escaping a gun attack at a rally that killed 20 supporters and damaged her hearing.
The Awami League, formed in 1948, traditionally offered socialist economic policies but she has moved it toward backing private sector expansion.