Tens of millions of Nigerians went to the polls despite fears that landmark presidential and state elections may be marred by violence or widespread ballot rigging. Crowds of voters queued in a peaceful but determined way at polling stations across much of the country, as Africa's most populous nation put its four-year-old experiment with democracy to the test.

"The electorate is more determined than ever before not to be taken for granted," said Titilayo Ajanaku, a popular local women's leader in the southwestern town of Abeokuta, amid a throng of around 200 voters.

The run-up to polling day has seen violent political tensions threaten to boil over, and security was tight as polls opened, with armed policemen escorting ballot boxes, and troops in the streets of major cities.

But in most of the country AFP reporters found polling better organised than at parliamentary elections on April 12, which were marred by fraud and violence, and voters were taking part in a cheerful and orderly way.

In the troubled southeast, however, problems persisted.

Polling began late in the southern and eastern states of Enugu, Rivers and Delta -- which monitors said were the scene of the worst of last week's problems -- raising temperatures outside polling stations.

"How do you explain a situation when they tell you after wasting more than one hour that ballot papers are missing?" demanded Jude Adikwe, a 32-year-old construction worker in Enugu town.

"I believe it is a grand ploy to rig the election ... but we will not allow this to happen," he said.

The April 12 polls, which produced a landslide victory for the ruling party of Nigeria's President Olusegun Obasanjo, were denounced by the opposition as "massively rigged" and criticised by independent monitors.

Obasanjo's main rival, former military dictator Muhammadu Buhari, has called on his supporters to come out to "defend their votes" at Saturday's presidential and gubernatorial polls, raising fears that mob violence could break out.

"Nigerians have to learn to be magnanimous in victory and gracious losers," said Obasanjo, as he cast his ballot in his hometown of Abeokuta.

There, as in the southwestern cities of Lagos and Ibadan and in the capital Abuja, AFP reporters found voters turning out in large numbers to vote in a relatively well-organised ballot.

Obasanjo appeared confident of victory -- "people feel we have done relatively well" -- and praised the improvement in polling conditions.

But in northern Nigeria, where Buhari has growing support among his fellow Hausa-speaking Muslim voters, the situation was more tense.

"I am really confident of victory. Maybe if you are in Kano you will see it better," Buhari told reporters in his far northern hometown of Daura while supporters cheered and chanted "Allahu Akbar" (God is great).

In the sprawling city of Kano large numbers of troops were deployed to enforce a ban on non-election related traffic, and wary groups of youths watched them from a distance.

In Kano many want change, and Obasanjo's supporters face a tough battle not just to deliver the city's four million voters to their leader but also to retain control of the state governorship.

"Just because I'm disappointed in the people I elected four years ago doesn't mean I'm going to give up voting," said 36-year-old Mariam Mahmud. "I will keep voting until the right leaders are elected."

Buhari, who seized power in a military coup in 1983 after Nigeria's last abortive attempt to hold a civilian-to-civilian transfer of power, was unrepentant over his call for popular resistance to ballot fraud.

"Mass action is a spontaneous action whenever a fraud takes place," he said after casting his vote. "I do not incite anybody. Obasanjo can say what he likes. I ask people to exercise their civil rights."

To secure the presidency without going to a second round in a week's time, a candidate needs to win a simple majority of the vote and at least 25 percent in two-thirds of the 36 states.

Aside from Obasanjo and Buhari, 18 more presidential candidates are taking part in Nigeria's broadest ever poll, but few of them are expected to have more than a local or regional impact on voting.

Nigeria's 36 states were also voting for governors Saturday, many of them in tight polls which observers feared could trigger violence.

PHOTO CAPTION

General Mohammadu Buhari, the All Nigeria People's Party presidential candidate, discusses his chances after casting his vote in the northern Nigeria Katsina state(AFP/Pius Utomi)