Millions of Nigerian voters are expected to vote Saturday in what is regarded as one of the most important national elections in the country's history. The vote follows state elections last week that provoked a storm of debate and concerns. Gilbert da Costa has this report from the Nigerian capital, Abuja.

Saturday's election is meant to consolidate democracy in Nigeria. But violence, and reports of voting irregularities that marred last weekend's state elections, have raised doubts about how credible the presidential vote will be.

Usman Mohammed, a political analyst in Abuja, says if the presidential vote goes the same way as the state elections, frustration at a stolen election could trigger widespread violence.

"Unless there is transparency, unless there is honesty, unless there is determination and the political will to carry out these electoral processes in due process and law, I believe the next election will be marred with violence. So, I understand very well the apprehension of every Nigerian."

The electoral commission has promised vast improvements in the conduct of the election.

Voters are choosing a new president to replace Olusegun Obasanjo, who is ending his second four- year term and is barred from seeking a third. The vote also would lead to the first democratic transition in Nigeria since its independence from Britain in 1960.

In a televised address Friday, the outgoing president urged Nigerians to keep faith with democracy despite the obvious flaws and glaring inadequacies.

"Do we have alternatives to democracy, no matter what difficulties we are encountering? The answer surely is no," he said. "Then, let us continue to improve on the structure and the house rather than pull it down because it is leaking in part. The world is watching us and we cannot afford to disappoint ourselves, our friends and the world."

Tensions are running very high in Nigeria ahead of the crucial vote, and the security forces will be fully stretched to oversee security in this huge, West African nation.

Police chief Sunday Ehindero says the police are poised to provide better security cover this time around.

"I think for the next election we will be better prepared than we were for this. It's not likely that you'll expect more violence in the next election, because this is the foundation for the presidential. And if this had been peaceful, I see no reason why the next one will not be peaceful," he said.

Analysts say Nigeria has not held free and fair elections since the end of military rule 1999. National and statewide polls in 1999 and 2003 were marred by widespread fraud and violence, as were local government polls in 2004.