ABUJA, Nigeria - Nigeria counted votes on Sunday after a crucial presidential election in Africa's most populous country.

Voters on Saturday were deciding whether to keep incumbent President Goodluck Jonathan, who took power after former president Umaru Musa Yar'Adua died following a lengthy illness in May 2010.

Voting was generally calm in most of the country, though three explosions hit the north - one on Friday night and two on Saturday - with several wounded.

Early results showed Jonathan had done well in much of predominantly Christian southern Nigeria, including areas such as the most populous city of Lagos, where his ruling party had struggled in a parliamentary election a week ago.

Among those looking to take away key votes from Jonathan in northern Muslim constituencies is a hometown candidate - former military ruler Muhammadu Buhari. He ruled Nigeria shortly after a 1983 coup. Former anti-corruption official Nuhu Ribadu is also running.

The electoral commission has said it expects to release full results within 48 hours after the end of balloting.

"Across the country it will be close," former government minister Nasir el-Rufai, a Buhari supporter, said at a vote counting center in the capital Abuja.

"My only fear is it will become a north-south issue if we see a situation where Buhari sweeps the north and Jonathan does well in the south. We may have to go to a run-off," he said.

To win in the first round, a candidate needs a quarter of the vote in two-thirds of the 36 states. There are more than 73 million registered voters and 120,000 polling stations.

A run-off between Jonathan and Buhari could risk polarizing voters along regional lines in the country of 150 million, where ethnic and religious rivalries bubble near the surface.

Jonathan told reporters on Saturday that Nigeria was experiencing a "new dawn" with the election, and that while he expected to win he would not interfere with the electoral process.

"I pray I don't go into a by-election because of the cost implications," he said wearing his signature black bowler hat and traditional caftan as he was surrounded by throngs of cameramen in his home state of Bayelsa. "We pray that whoever will win, will win."

AP-AFP-Reuters