Khartoum - Two independent candidates withdrew from Sudan's presidential election on Wednesday, citing irregularities in the polling process after the election commission extended voting by a day.
Most of the main opposition parties had already boycotted the election, which started on Monday and had been due to end on Wednesday, saying they had been denied the opportunity to compete fairly against President Omar Hassan al-Bashir, in power since 1989.
With little effective opposition, Bashir appears certain to be re-elected. A parliamentary election is also being held.
"There are legal irregularities in the election and regulations. The National Election Commission wants the ruling party to win the elections in whatever way possible," candidate Ahmed al-Radi Jaber told reporters after announcing his withdrawal.
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He said the decision to extend voting until Thursday was an attempt to manipulate the result. The commission said that logistics problems had hampered voting in some areas on Tuesday, and that the extension was intended to ensure that everyone had the opportunity to vote.
A second independent candidate, Omar Awad al-Kareem Hussain, also withdrew, cited problems with voting papers and the balloting process, calling the election a "political farce".
At least 13 million Sudanese are eligible to vote. The boycotts and withdrawals mean that they have few alternatives to Bashir and his National Congress Party (NCP), other than a handful of relatively new groups.