Voting has officially ended across Nigeria in a presidential vote dogged by violence, charges of fraud and logistical problems. Gilbert da Costa reports for VOA from Abuja that election officials say results are expected in a few hours.

Electoral Commission Chairman Maurice Iwu spoke to reporters shortly after the polls officially closed.

He said the exercise had been reasonably successful. "So far, I will say, so good. We had a late start in the southeast, because their plane came in late. We anticipated such things could happen. The critical message is that our people are interested in casting their vote, the commission is determined to make sure that their votes count," he said.

But voting is continuing beyond the official closing time. The Independent National Electoral Commission, known as INEC, has authorized flexible voting hours due to delays in distributing 65 million ballots across the vast country of 150 million.

Turnout was generally satisfactory across the country, although a few voting centers were virtually empty.

At Mpape, a sprawling settlement outside Abuja, only about 60 voters, out of 500 who were registered, turned up. An electoral officer who gave his name as Kingsley explained. "Those who registered here are mostly civil servants. The reason for their registration was that, maybe, the government might require them to present it before they are paid their salary. But, they said they will not vote. We've registered about 60 people," he said.

As with state elections last weekend, a number of candidates for the federal parliament were shocked to find their names missing from the ballot.

Progressive Action Congress Chairman Agade Nwodo was upset that his party's senate candidate from Abuja did not appear on the ballot. "We discovered that on the ballot paper, the Progressive Action Congress, one of the political parties contesting elections in the FCT [Federal Capital Territory], is omitted. It is a big shock to us. He underwent all the processes for screening and documentation and was listed. He has been campaigning seriously and spending money and mobilizing people. At the end, he is frustrated on this particular day," he said.

The government says it is investigating an attack on the electoral commission's headquarters on Saturday, shortly before voting began.

Seven police officers on election duty were killed in an ambush outside Abuja late Friday night.

The opposition Action Congress says Saturday's elections were rigged. The other opposition parties have yet to comment.

The election is expected to produce the first handover from one civilian president to another since Nigeria's independence from Britain in 1960.