There have been adverts for identity cards
Major problems have been reported on the first day of registrations for Nigeria's national identity card scheme.
Lack of equipment and publicity were blamed by some Nigerians.
People reported problems finding some of the 60,000 centres set up for registrations.
Others said some centres do not have the equipment to register them.
About 60 million Nigerians are eligible to register over the next two weeks.
The importance of the programme cannot be over-emphasised
Nigeria is Africa's most populous country, with an estimated 120 million inhabitants, including many immigrants attracted by the country's oil industry.
President Olusegun Obasanjo said the scheme would help with the identification of illegal immigrants and provide data for government planning.
However, some northern politicians oppose the scheme, fearing it will be used to cross-check other population records, including the voters roll.
Correspondents say that population figures are often inflated in order to increase access to government resources.
Some southerners say that the population in the north is far lower than official figures suggest.
Such argument have delayed a census, which was supposed to have been conducted in 2001, 10 years after the last one in 1991.
The BBC's Mannir Dan-Ali in Abuja says that he only saw one registration centre open and it was extremely disorderly.
Deputy Interior Minister Odion Ugbesia said that "foolproof" measures have been taken to prevent fraud, double registration and foreigners from getting Nigerian identity cards.
The cards will include fingerprints and photographs, as well as the name, address, occupation, state of origin and height of the bearer.
The idea of a national identity card was first mooted in 1978 by current President Olusegun Obasanjo, who was then Nigeria's military ruler.
Several contracts to produce identity card have been cancelled following changes of power, amid allegations of fraud.
Mr Obasanjo says that the scheme will help government planning and to fight fraud and corruption.
"The importance of the programme cannot be over-emphasised in the country," he said in a recent interview.
It will not be obligatory to have an identity card but correspondents say that it might be necessary to obtain government services.
Officials deny that it is linked to the forthcoming election in April.