KADUNA, Nigeria - Nigerian President Goodluck Jonathan won nearly every state in preliminary results released Sunday for the oil-rich nation's presidential election, though fragmented returns suggested he faced strong opposition from the country's Muslim north.

Meanwhile, authorities in this northern Nigerian city and hometown of the country's vice-president said eight people were wounded after a bomb exploded at a hotel in a poor neighbourhood hours after voters cast their ballots.

Jonathan, who became president after his predecessor died in office last year, remains the presumed front-runner in Saturday's poll as his ruling People's Democratic Party has dominated politics in the West African giant since it became a democracy 12 years ago. But to become president, he must carry at least a quarter of the votes cast in at least 24 states and its capital.

Results released Sunday by Nigeria's Independent National Electoral Commission show Jonathan won the capital of Abuja and 11 states. He also carried more than 25 per cent of the vote in two others.

However, none of these initial returns included any states from Nigeria's north, which remains hesitant about Jonathan as the Christian from the south who took over after the death of the country's elected Muslim leader. Many of the north's elite wanted the ruling party to honour an unwritten power-sharing agreement calling for a Muslim candidate to run in this election.

Former military ruler Muhammadu Buhari, the presidential candidate of the Congress for Progressive Change, won the support of many in the north as a Muslim leader willing to crack down on the corruption prevalent in the nation. Initial results not yet certified by federal officials suggested he carried several northern states.

Nigeria has a long history of violent and rigged polls, and legislative elections earlier this month left a hotel ablaze, a politician dead and a polling station and a vote-counting centre bombed in the nation's northeast. However, observers largely said Saturday's poll appeared to be fair, with fewer cases of ballot box thefts.

"These elections were not without problems -- in particular isolated incidents of intimidation, violence, and illegal voting -- but these did not undermine the overall credibility of the process," read a statement issued Sunday by Project 2011 Swift Count, a coalition of trusted local monitoring groups.

The tension between Christians and Muslim has erupted into violence that has killed thousands since Nigeria became a democracy more than a decade ago. Many of those attacks focus in Nigeria's fertile central belt.

In the city of Kaduna -- the hometown of Vice-President Namadi Sambo and one city that's been at the centre of that violence -- police said Sunday that officers had two suspects in custody after the bombing Saturday night at the Happy Hotel. Kaduna state police spokesman Aminu Lawal told The Associated Press that authorities had no motive for the attack, though the neighbourhood suffered some unrest during voting Saturday.

Inside the hotel, police officers looked for evidence Sunday amid the crumbled cement walls, shattered glass and bloodstained ground. The explosion happened just next to a small dingy bar inside the hotel complex, which on one wall bore a sign that read: "This brothel supports no condom, no sex policy."

Outside, a giant Jonathan campaign banner hung over the hotel in a neighbourhood home to both poor Christians and Muslims. Blue graffiti bearing the name of Buhari's party could be seen on walls, while other ruling party banners appeared to have been cut with knives.