There were chaotic scenes at some polling centers - south Sudan's president Salva Kiir had to wait 20 minutes under a tree for his voting station to open in the southern capital Juba and ended up spoiling his first ballot by putting it in the wrong box.
Queues started forming in the morning in Khartoum, where the streets were unusually quiet amid a heavy police presence and there were reports of delays in other areas.
Sudan's police said they would deploy 100,000 officers across northern Sudan to guard polling stations and ward off unrest during three days of voting to choose a national president, a leader for the semi-autonomous south, assemblies and governors.
Sudan's incumbent president Omar Hassan Al-Bashir, who faces an arrest warrant from the International Criminal Court for allegedly planning war crimes in the western Darfur region, seems certain to win another four-year term after leading opposition parties pulled out of the race.
"We know that there are no perfect elections, and these polls will not be an exception to that rule," said Abdallah Ahmed Abdallah, a top official at Sudan's electoral commission.
"These elections will not suddenly transform Sudan into a democratic society. That will take time and experience." Opposition groups and activists say even such modest expectations will go unmet as they put forward myriad complaints of vote-rigging and other misdeeds, fueling doubts about the credibility of Sudan's first multi-party polls in 24 years.
VOTING PROCESS In Khartoum, voters stood or sat in long lines for more than an hour to go through the complex voting process - electors receive eight voting forms in the north and 12 in the south.
Men and women waited in separate lines and had to dip a finger in indelible green ink before voting.
One of the voters in the capital's Riyadh district, El-Fatih Khidr, a 55-year-old pilot, told Reuters authorities should have opened more voting centers to cope with the crowds.
"There are a lot of crowds and there should have been more information because there is a whole new generation that have never voted," he said.
There was a palpable sense of excitement on the streets of Juba, where many see the elections as a prelude to a referendum on southern independence scheduled for January 2011. Both votes were promised under a 2005 peace deal that ended more than two decades of north-south civil war.
"This is my first time to vote and it is a good beginning that Sudan is going back to democracy. I hope it will be a foundation for future democracy," said South Sudan's president Kiir after voting.
Up to 300 women in bright clothes were among voters who waited patiently for more than an hour in the southern town of Malakal as officials tried to find vehicles to deliver voting forms, said a Reuters witness.
In Sudan's western Darfur region, the scene of a seven-year conflict between government militias and rebels, aid groups moved staff out of remote areas to cities in case of unrest.
"We're not expecting widespread violence, only things that might blow up in pockets," an aid official told Reuters, speaking on condition of anonymity.
"Everyone is prepared to hibernate if there is any trouble ... People have stocked up their houses with food and water." In Khartoum, bus companies added vehicles as a huge number of residents poured out of the city, some of them fearing possible election reprisals and others simply happy to take advantage of the three-day election to visit home villages.
"I was scared, but now that these (opposition) guys have withdrawn there's no competition with Bashir," said Khartoum housewife Atouma Hassan.
