Southern former rebels called for polling to be extended in Sudan's first multi-party vote in two decades yesterday as the electoral comission acknowledged "mistakes" in distributing ballot papers.

The Sudan People's Liberation Movement (SPLM) said it had asked for polling to be extended from three to seven days after what it described as a "wasted" first day marred by procedural problems across Africa's largest country.

"There have been a lot of irregularities that we have noticed," said Samson Kwaje, campaign manager for SPLM leader Salva Kiir.

Mr Kwaje said the irregularities included polling stations opening late, wrong ballot boxes in the wrong places and ballot boxes going missing. The National Election Commission acknowledged there had been "mistakes" in distributing ballot papers in some areas but made no comment on the possibility of prolonging the election. It said the process was going well "except some technical mistakes about the distribution of ballots in 26 centres in Khartoum state."

"In White Nile state, there has been a problem matching the symbols with the candidates," it added.

The polling process had always threatened to be difficult with an electorate with a high level of illiteracy contending with multiple ballots for simultaneous presidential, parliamentary, state and southern regional elections.

In the southern regional capital Juba, voters said they struggled with no fewer than 12 ballot papers.

But the complaints compounded question marks about the credibility of an election from which key candidates had already withdrawn ahead of polling day citing fears of fraud.