KABUL, Oct 9: Afghanistan's first-ever presidential election was thrown into confusion on Saturday after all of President Hamid Karzai's rivals said they were boycotting the poll because of irregularities.

The move by 15 of the 18 candidates in the fray effectively leaves Mr Karzai as the only one standing - two others withdrew in his favour earlier this week. The boycott decision was made at an emergency meeting during voting.

It was not immediately clear how much credibility the poll would have after the boycott or whether it would lead to further divisiveness in the country.

"Today's election is not a legitimate election. We are not a part of today's election," contender Abdul Satar Serat said after a meeting of most of the 15 candidates and the representatives of the others.

"We want the elections to be re-held as soon as possible in a fair, transparent manner and without interference. Any government that comes to power as a result of today's election has no credibility, no validity and is illegitimate for us."

Mr Serat, flanked by all those who attended the meeting, accused election authorities of favouring the US-backed Karzai and not being able to prevent multiple voting.

Opposition candidates alleged that people voted several times with multiple cards, polls closed prematurely in areas populated by opposition supporters, and that voters were pressured to choose Hamid Karzai. Even the sole woman candidate Masooda Jalal, the only opposition candidate not to join the boycott call, alleged 'planned and organised fraud'.

There had earlier been widespread complaints that the wrong pens were being used to mark voters' fingers to show they had cast their ballot, and what should have been indelible ink could be quickly wiped off.

Senior election officials from the Joint Election Management Body (JEMB) were meeting to discuss the boycott, said one official.

The organizers of the first direct presidential election in Afghanistan's history had earlier insisted that voting would continue despite the complaints.

"The JEMB has made the decision that voting continues throughout the country," Manoel de Almeida e Silva, the UN's chief spokesman for Afghanistan, told a news briefing.

Officials said the complaints were the result of a minor misunderstanding - the pens used to mark ballot papers had been mistaken for those used to mark voters.

"The workers have got two pens which look alike," said Reg Austin, a senior technical adviser with the JEMB. "One is for marking ballots and other is for indelible ink. Workers are using the wrong pen.

"We believe the scale of the problem is relatively small," Mr Austin added. "We would assume it is in the process of being corrected."

Leading presidential candidate Yunus Qanuni - one of the candidates at Satar Serat's meeting - had earlier told reporters he would not vote unless something was done to resolve the situation.

"We need to discuss this issue very urgently," Mr Qanuni told reporters.

"If this continues, the election in Afghanistan will not have any credibility. I am looking for a solution for all the candidates. If we find a solution we will go forward, if not, we will not vote."

Election officials refused to halt the process, which appeared to have been embraced enthusiastically by most voters despite fears that many would be too afraid to participate.

"Halting the vote at this time is unjustified and would deny individuals the right to vote," said election official Ray Kennedy. He said the allegations would be investigated but other officials said it could take weeks to complete the process.

Hamid Karzai also said the vote could not be negated. "It's too late in the day for a boycott," he told a news conference. "Millions have voted in the rain, the snow and the dust and we should respect their decision.

"It is too late to call for a boycott now that millions of Afghans have come from their homes despite rain and snow and they have voted," the US-backed candidate told a news conference.

"We should respect the people's will. I'm very delighted that all over Afghanistan, with the help of God, people with a lot of happiness and enthusiasm went to ballot boxes and voted.

"This shows the political understanding of Afghans and their will for a peaceful future."

During the campaign, some candidates expressed surprise that as many as 10.5 million out of the country's 28 million people had registered to vote, and said they believed many people had received multiple voter cards. -Agencies