When Nigeria holds its first headcount in 15 years, beginning Tuesday, the West African nation will be hoping to put to rest speculation about its true population. Gilbert da Costa reports from Abuja on the challenges that could mar the process.

Governments in the past have been accused of manipulating figures for political ends. The distribution of federal government funds to Nigeria's 36 states is largely based on population figures.

In an attempt to minimize objections to the result on tribal and religious grounds, the authorities excluded faith and ethnicity from the questionnaire.

Census officials were also appointed to states far away from their home states.

Christian leaders are particularly upset by the exclusion of faith from the census. And even though they have dropped their boycott threat, they still have serious reservations.

"It is most unfortunate that the government has taken a position on these crucial issues because everywhere, it is necessary for us to know who we are and what group of people ... what is our background and things of that nature," said Jerome Bello, the chancellor of the Catholic Church in Abuja. "I think it is very, very important for us to know how many Christians, how many Muslims we are in this country. How many other traditional religions we have in this country."

The credibility of the census is being threatened by heightened political tension ahead of elections next year.

Nigeria has about 250 ethnic groups, each demanding a voice in the politics of the country. Some communities have rejected census officials posted to their area, insisting on the appointment of indigenous officials.

Despite the enormous challenges in carrying out a credible census in Nigeria, the chairman of the National Population Commission, Sumaila Makama, told VOA that the body is ready for the five-day exercise that begins Tuesday.

"The good news is that as of now, we do not have any serious complaints or threats of boycott," he said. "I have not received any report from any state that any group is boycotting the census. Rather, community leaders are appealing to their people to make sure that they get counted because if they are not counted, that will distort the demography in their areas."

About 820,000 field workers have been recruited for the census. The total cost of the exercise is estimated at about $260 million. The European Union, which has sent 90 monitors, provided a grant of $150 million.

The last census in Nigeria in 1991 put the country's population at 88.5 million. Based on a projected annual growth of about three percent, the population is currently estimated at between 120 and 150 million people.