"We have followed some of the voters through the process, which is very tedious and complicated."
Mohamed Vall, Al Jazeera's correspondent at the Abu Shoq displacement camp in western Darfur, said: "The polling stations opened an hour late and voting started at a very slow pace."
He said that only about 7,000 of the camp's some 55,000 residents are registered to vote.
Southern Sudanese are also voting to elect a leader of the semi-autonomous government of the south.
Omar al-Bashir, the incumbent president, is almost certain of victory in the presidential race after opposition candidates pulled out, alleging widespread bias against them in the electoral system.
Yasser Arman, a northern Muslim representing the former southern rebel Sudan People's Liberation Movement(SPLM), and Sadiq al-Mahdi of the Umma Party,have both withdrawn from the race.
They accuse al-Bashir of fraud and say free and fair conditions for the elections are not in place, particularly in Darfur, the western region under a state of emergency since civil war broke out seven years ago.
Darfur rebel movements, who control parts of the vast region, firmly rejected the elections but have so far not stated any intentions to derail the process.
While the result of the presidential poll holds little suspense, elections for parliamentary and local representatives are still fiercely competitive in many parts of the country.
Activists cautioned on Saturday that the credibility of the election had been undermined by the allegations, which they said have been ignored by al-Bashir's ruling National Congress Party(NCP).
"Violations of human rights - particularly restrictions on freedom of assembly and freedom of the press - are threatening prospects for a free, fair and credible vote across Sudan," Georgette Gagnon, Africa director of Human Rights Watch, said.
"Sudanese authorities are clearly failing to uphold international standards."
Election organisers rushed on Saturday to get ballot papers to the more remote parts of the country.
|Poll organisers have rushed ballot papers to more remote parts of the country [Reuters]
Sixteen airplanes, 16 helicopters and more than 2,000 vehicles were mobilised in the past two weeks to transport ballot boxes around the country.
"I hope that it will be completely compatible with international standards, and safe and free and fair, and that the decision of individual voters will be expressed freely without intimidation," Jimmy Carter, a former US president, whose Carter Centre is monitoring the three-day vote, said.
Security forces have been deployed in strength, as have international peacekeepers in both the war-torn western region of Darfur and in the south.
More than 100,000 police officers will be on duty, a security official said, and embassies in the capital Khartoum have advised their nationals to adopt precautionary measures such as stocking up on food and fuel.
Hopes have dimmed that the elections will be a watershed moment as Sudan attempts to put decades of conflict behind it.
Last-minute boycotts have revealed the fragility of the 2005 peace dealthat ended the country's long North-South civil war.
The NCP has ruled Sudan in a coalition with the SPLM since the signing of the peace agreement.
|The elections are seen as a step towards the South's referendum [Fatma Naib/Al Jazeera]
Part of that deal was an agreement that Southern Sudan could hold a referendum on independence and many in the south see these elections as a step towards that goal.
Even though polling stations opened late, people arrived two hours before the official opening of polls, Hoda Abdel-Hamid, Al Jazeera's correspondent, reporting from the southern city of Juba, said.
"Everyone here in the south is excited about the referendum and the vote."
"The people here are looking at these elections as a stepping stone to reach the referendum."
Analysts said on Saturday that renewed violence over the outcome of the coming election is a distinct possibility.
"If elections are to take place in such compromised environment, conflicts about the legitimacy of the results might spark violence," the African Centre for Justice and Peace Studies said in a statement.