Sudan on Tuesday shut down for its first census in 15 years, a milestone in the peace deal that ended Africa's longest civil war but overshadowed by a dispute that threatens to undermine the accord. In the 2005 agreement signed by the former warring north and south, the two-week census is crucial to prepare constituencies for national elections and confirm or adjust the wealth and power-sharing ratios in central government.
But the undeveloped south has refused to be bound by the results and rebels in Darfur will boycott the count, both accusing the Arab north of manipulating the census to maximise its control and marginalise the African majority.
Khartoum, assisted greatly by the United Nations, said the door-to-door counting was smooth and transparent for the most comprehensive census ever held in Sudan, almost constantly engulfed in civil war since independence from Britain in 1956.
Rain fell in Khartoum -- almost unheard of in April. Shops and businesses were closed, and streets largely deserted with people told to stay indoors.
Heavy rain also fell in the south until early morning. One plane of monitors was unable to land overnight in the southern city of Rumbek because of flooding.
"We have some challenges but I think there is a will to overcome these challenges," said Abdel Bagi Gailani, whom the presidency appointed to head the monitoring and observation committee.
Around 60,000 enumerators dressed in pale blue baseball caps and jackets, monitored by 200 observers, will count the estimated 40 million population, costing Sudan and the international community 103 million dollars.
"So far everything is going smoothly. We are not predicting any problems either today or in the coming days," said Ibrahim Abbas, the head of the census in northern Sudan.
But discontentment and disillusionment run deep in the south, where the legacy of the war that killed two million people and displaced another four million, is keenly felt despite a flood of refugees returning for the count.
"The level of preparedness was very low and even if counting takes place (Tuesday) its not going to produce the desired results," south Sudan information minister Gabriel Changson Chang told AFP.
His government said it was unlikely to accept the results after the north insisted the survey go ahead. It was delayed for the fourth time last week when the south complained that ethnicity and religion were not included.
The Arab domination of power in what is Africa's largest country was a major reason for the two-decade civil war between north and south, as well as for the separate five-year conflict still raging in the west.
International observers have raised concerns that significant parts of Darfur -- a region the size of France -- and not just three percent as claimed by Khartoum will be excluded from the count owing to opposition from rebels.
Khalil Ibrahim, the leader of the Justice and Equality Movement, the strongest rebel group militarily in Darfur, told AFP he "did not know" when asked if his followers would stage attacks to scupper the census.
"My people are not there at home, many of them crossed borders. They're in Chad and concentrated in IDP camps, under trees here and there, in mountains and villages, so what they're doing is meaningless," he added.
The Egyptian-occupied Halayib triangle in the northeast and remote areas in the south flooded by rains will also be excluded, although Isaiah Chol, the head of the southern census, said enumerators have 55 boats to ease access.
The schedule for implementing the Comprehensive Peace Agreement, under which general elections should have been completed by July 2009, is slipping. Under the accord, the census should also have been finalised last year.
Borders between north and southern Sudan have not yet been demarcated and political tensions remain high in the contested oil-rich state of Abyei.
UN Secretary General Ban Ki-moon warned that further delay of the census "could have considerable political and financial implications".
The central bureau of statistics expects census results as early as September, but other officials have quoted Christmas as a more realistic date.