Officials in southern Sudan have raised concerns about the validity of the initial results from last year's national census. 

The census was conducted last April, to update Sudan's population figures, as the country heads into national elections in 2010 and a referendum the following year on whether southern Sudan will become an independent state.  The figures will also be used to determine how to share power in Sudan's national unity government and how to distribute the country's oil wealth.

Sudan's last census was held in 1993.  In addition to the usual demographic changes one would expect in 16 years, the country has experienced more than a decade of war between the north and south, as well as another conflict in the western Darfur region.  Hundreds of thousands of people have been killed and far more displaced.

The census is of particular concern for the south, which claims that an accurate census has not been conducted in the region since 1956.

This week, the government announced preliminary results, saying the population of the country was slightly more than 39 million people and that the capital, Khartoum, is the most populous province.  The government has not yet released a breakdown of where the population is located.

But the head of the southern Sudan census commission, Isaiah Chol Aruai, tells VOA the South is concerned about several components of the results, including the figures for Darfur.

"The figure of Darfur, as a region, we think it is high, given the fact that there has been some insecurity in the area for quite a while.  And, if we also compare the figures of 1993 with the 2008 figures, there is a very big gap.  So we are questioning the validity of those figures," said Aruai.

According to unofficial results, published in the local media, Darfur's population was reported as 7.2 million people, compared to three million in 1993.

Aruai also says the figures for nomadic populations were higher than expected.  The status of nomadic Arab groups in the disputed border region between north and south, where much of the country's oil is found, has long been contentious.  For example, in the Abyei region, the north has attempted to count Arab cattle herders who pass through the area as residents.  Because they have tended to side with the north, an increase in their numbers could help boost the north's claims to the area.

Additionally, Aruai says the census may have undercounted the number of southerners currently living in northern Sudan after being displaced during the war.

"The population of the southern Sudanese in the 15 states in the north, we consider it to be significantly less than what the international NGOs (non-governmental organizations) for the IDPs (internally displaced persons) have been talking about," said Aruai.

Southern officials have said they believe the south should account for a third of the country's population, which would mean an increase of about five million people from the 1993 figure of eight million.  But, according to the figures published by local media, the latest census again puts the south at slightly more than 20 percent of the population.

Southern officials have threatened to boycott next year's national elections, if they consider the census results unacceptable.

Official census results are set to be announced after approval by Sudan's presidency.  Under the 2005 peace agreement that ended the north-south war, the president of semi-autonomous southern Sudan, Salva Kiir, serves as vice president in the national government, alongside President Omar al-Bashir.