国际英语新闻:Buhari Officially Declared Winner of Nigeria Presidential Election

Some of Buhari's victories came in states in southern Nigeria, which is generally considered a stronghold for Jonathan.

Tensions persisted in Port Harcourt, in the oil-rich Niger Delta region, where officials declared a dusk-to-dawn curfew. Rivers state has been the scene of some post-election protests.

The All Progressives Congress has called for the election there to be redone after alleged vote-rigging.

Jega, however, said Tuesday that commission investigators found no "substantial grounds" to cancel the vote there.

Post-election violence marred the country's disputed 2011 vote, resulting in about 800 deaths, mostly in the nation's northern regions.

On Monday, U.S. Secretary of State John Kerry and British Foreign Secretary Philip Hammond released a joint statement saying there were "disturbing indications" that the collation process "may be subject to deliberate political interference."

'Acceptable' Voting

International observer missions had called the conduct of the voting "acceptable," despite technical glitches in a new computerized, anti-fraud system that prompted officials to extend voting by a day.

Nigerians across the country appeared to be closely watching the commission's work, broadcast live on national TV.

"There’s tension right now in Lagos because people are anxious to have the results. People are anxious," said David Olayemi, a Lagos resident. "They are waiting for the results, for the announcement of the new elected president."

In the northern city of Kano, where men sat drinking tea and listening to a radio, Abdul Rashid Sani said he suspected the government was up to something. He said the results from previous elections came faster, but he was confident that his party, the All Progressives Congress, will win.

In Kaduna, Al Amin Jinge also voiced concerns about the outcome.

"Everybody is afraid of the announcement of result. That’s why everybody hide at home," he said. "But we pray so nothing will happen, that, God willing, there is not any violence."

Nigeria's election originally was scheduled for mid-February, but officials pushed back the vote because of fighting and instability in northeastern states where Boko Haram militants have been battling the government since 2009.

The security situation improved after a multinational offensive drove the militants from many towns they had controlled.