Efforts to distribute voter registration cards in Nigeria appear to be off to a slow start before elections later this month.
Voters in Nigeria's main city, Lagos, complained that they had yet to receive their voter registration cards, only a few days before the start of general elections.
More than 60 million Nigerians are eligible to cast ballots in legislative elections that are scheduled for this Saturday, and presidential elections that are due to take place on April 19.
The drive to distribute voter cards officially got under way on Tuesday, but observers said many of the centers that were to give out the cards had yet to open.
Officials of Nigeria's Independent Electoral Commission said there had been anormalies in the distribution process that had been caused by staff shortages. But officials said the problems were isolated to some districts across the country.
Word that not everyone had received their voter registration cards just a few days before the first poll spread worries that the polling might not go as smoothly as the government would hope.
A bout of ethnic fighting in the oil-producing areas of the Niger River Delta last month triggered concerns about stability in Nigeria ahead of the elections.
On Tuesday, a group of minority parties called for postponement of the poll, citing what they claimed was a lack of organization and what they described as general instability in the country.
The elections in Africa's most populous nation will be the first to be held since the transition from military rule to a civilian government in 1999.
President Olusegun Obasanjo will face more than a dozen challengers, the most prominent of whom is Muhammadu Buhari, a former military ruler popular in Nigeria's largely Muslim north.