The BBC's Barnaby Philips: The APP and AD may join forces in the presidential elections

As the results were being declared, Commonwealth Secretary-General Emeka Anyaoku said Nigeria was well on course in its transition from military to civilian rule.

The PDP - led by former military ruler and presidential hopeful General Olusegun Obasanjo - was the clear winner, with 20 of the 35 state governorships up for grabs.

But the party did not repeat the resounding success it had in last month's local elections. The centre-right All People's Party (APP) won the governorships of several northern states.

Led by supporters of the late military ruler General Sani Abacha, the APP took nine seats.

The radical Alliance for Democracy, mainly composed of ethnic Yoruba opposition politicians, swept all six states in its south-western stronghold, including the capital Lagos.

The city's governor-elect, Bola Tinubu, is a former exile who only returned to the country after the sudden death last year of General Abacha.

General Obasanjo casts his vote

The Alliance for Democracy made little impact elsewhere.

Saturday's vote in 35 of Nigeria's 36 states is seen as an important prelude to the country's return to democracy.

Only three parties earned enough votes in December's local elections to qualify for the state polling.

BBC Correspondent Barnaby Phillips: Few reports of electoral fraud or violence

Many voters in Lagos said they were impressed by how smoothly voting proceeded.

Elections did not take place in oil-rich Bayelsa, which has been the scene of growing violence by members of the Ijaw tribe.

There was disappointment that the voter turnout appears to have been lower than in December.

Anti-fraud measure

The Commonwealth observer mission in Nigeria said voting procedures had improved since last month's local elections.

The electoral commission faced an enormous task, organising about 100,000 polling stations in a country whose infrastructure is in a woeful state of disrepair.

In a novel anti-fraud move, voters were allowed to stay at polling centres after they had cast their ballots to watch votes being counted.