DHAKA (AFP) - Bangladesh's opposition leader Khaleda Zia accused Prime Minister Sheikh Hasina of "murdering democracy" as her arch rival faced growing calls on Tuesday to hold fresh polls after a walkover election.

The United States led international pressure for a swift re-run that would include all the major parties, brushing aside Ms Hasina's insistence that a boycott by Ms Zia's opposition did not undermine her legitimacy.

Ms Zia, who has been confined to her home for about two weeks, reiterated her calls for the prime minister to stand aside and let a neutral caretaker government organise the new election.

"I'm calling on the government to cancel the farcical polls, step down and reach an understanding (with the opposition) to organise a free, fair and neutral election under a non-party government," she said in a statement released overnight.

"The scandalous election on January 5 not only demonstrated the people's lack of confidence in the government but also proved that free, fair, credible, peaceful and participatory elections cannot be held without a non-party neutral government and credible election commission."

At least 26 people were killed during Sunday's election, the bloodiest vote in Bangladesh's history, while hundreds of opposition supporters set fire to or trashed polling stations.

The result was never in doubt, with Ms Hasina's Awami League and a handful of allies winning all the seats being contested.

The vote's credibility had been undermined even before polling day as 153 Awami League members or allies were declared elected unopposed to the 300-seat parliament.

In a defiant appearance before the press on Monday, Ms Hasina rejected any idea that her legitimacy had been compromised by the absence of Ms Zia's Bangladesh Nationalist Party (BNP) and 20 other opposition parties.

But Ms Zia, in her first comments since the election, said the Awami League had no "moral or constitutional grounds" to hold on to power.

The United States also called for a new vote that would "credibly express the will" of the people.

"With more than half of the seats uncontested and most of the remainder offering only token opposition, the results of the just-concluded elections do not appear to credibly express the will of the Bangladeshi people," said State Department deputy spokeswoman Marie Harf.

"While it remains to be seen what form the new government will take... we encourage the government of Bangladesh and opposition parties to engage in immediate dialogue to find a way to hold as soon as possible elections that are free, fair, peaceful, and credible."

UN leader Ban Ki Moon was "saddened by the loss of life", his spokesman said. Mr Ban called for the two parties "to resume meaningful dialogue and to urgently address the expectations of the people of Bangladesh for an inclusive political process".

There was also criticism from the former colonial power Britain, with junior foreign minister Sayeeda Warsi saying "the true mark of a mature, functioning democracy is peaceful, credible elections that express the genuine will of the voters".

In a defiant press conference on Monday, the prime minister said the opposition election boycott should "not mean there will be a question of legitimacy".

"People participated in the poll and other parties participated," she added in reference to a handful of Awami League allies who did stand.

Asked about the prospect of sanctions on her government, Ms Hasina was dismissive, saying: "What crimes did we commit that they would impose sanction on us?"

She also made clear she was in no mood to extend any olive branches to Ms Zia, her bitter rival for the last two decades, accusing the two-time former premier of stoking the violence.

"If they come forward to discuss with us, they have to leave all these terrorist activities behind because what they are doing, it is absolutely killing people, killing police, killing innocent people."

Any agreement on a new vote carries huge risks for Ms Hasina, with an eve-of-election poll showing she would have lost in a straight contest with the BNP.

Analysts expect the standoff will fan the flames after the deadliest year of unrest since Bangladesh broke free from Pakistan in 1971.

Since late October, around 180 people have died in electoral violence in a country that has experienced nearly 20 coups since independence.