(CNN) -- Counting was under way in Sudan on Friday, nearly a week after voters started casting ballots in the nation's first multiparty election in 24 years.
Sudan's election commission extended the vote for two days past the original Tuesday deadline after observers complained of technical problems, including ballots being sent to the wrong polling stations and registers missing voters' names.
Zach Vertin, an election observer for the International Crisis Group, said the results could be announced in a few days.
"The best-case scenario is by April 20, but it could also take longer," Vertin said.
The most important thing is that candidates wait peacefully, avoid triggering any violence and make sure they communicate the process to their supporters, he said.
"Any disputes should be addressed by the mechanism set up by the election commission," Vertin said.
The voting, which began Sunday, was for president, parliament and other local positions. About 750 international and 18,000 domestic observers monitored the process.
Opposition parties accused the ruling National Congress Party of fraud, prompting some parties to withdraw partially or fully from the vote.
Sudan People's Liberation Movement, the main party in the south, sought an extension to the vote. The party recently withdrew its presidential candidate from the race against President Omar al-Bashir. The incumbent has denied allegations of fraud.
Former U.S. President Jimmy Carter, who was an observer, criticized parties that pulled out of the race and said the United Nations and Washington had urged them not to.
"You have to remember two things: one is they withdrew basically after the campaign period was over at the last minute and they have known about these problems for months," he said.
It was too late for them to quit the race legally, he added.
"The last date was back in February, when they could have withdrawn legally. They didn't do so."
The election was a key part of a 2005 peace deal that helped end decades of civil war between the country's north and south. The conflict pitted Christian and Animist southerners against Muslim northerners, leaving more than 2 million people dead. The peace deal also called for a referendum next year to determine whether the south should become an independent nation.
Analysts have said that since most of the oil is in the south, a divided Sudan could negate sanctions to allow companies to prospect more easily in the south.
Al-Bashir has ruled Sudan since a 1989 coup. He is wanted by the International Criminal Court for alleged war crimes in a genocide in the western Darfur region. The Darfur conflict is separate from the north and south war, and is between government militias and ethnic rebels.
The president's implementation of Islamic law created divisions between the north and south of the oil-rich nation.
CNN's David McKenzie contributed to this report.