|Violence erupted in the north after Goodluck Jonathan was declared winner of the presidential election [EPA]
Counting is under way in Nigeria following elections for the country's state governorships.
The vote count on Wednesday came amid reports that gunfire and ballot box thefts may have led to low voter turnout a day earlier in some polling areas.
Al Jazeera's Yvonne Ndege, reporting from Kano in northern Nigeria, said at least one state in the north, Gombe, had election officials fleeing polling units due to violence on Tuesday.
"We're still waiting for the results to start trickling in. Security forces are poised to clamp down on any violence that might erupt," she said.
"All of this is happening against the backdrop of a week of post-election mayhem in which at least 500 Nigerians have been killed and some 74,000 people displaced," she said.
|Al Jazeera's Yvonne Ndege reports from Kano
Tuesday's vote for governors followed legislative and presidential elections earlier this month.
But those votes were following by intense fighting that erupted in the north after Goodluck Jonathan, a southern Christian, was declared winner by a wide margin in the April 16 presidential election.
Supporters of his northern opponent Muhammadu Buhari rejected the results and took to the streets. Hundreds of people died in the ensuing violence and churches, mosques and homes were set ablaze.
Election officials postponed the governors' races in the two northern states hardest hit by post-election violence but had vowed to press ahead with voting in 36 other states.
Some suggested this week's voting for state governors and state assemblies be postponed to allow tempers to cool, but Jonathan said the polls would go ahead despite the violence.
"This was a public declaration that he won't let anything stand in the way of completing this election cycle," Patrick Mmeme, a public policy analyst and writer, told the Reuters news agency.
State polls have in the past led to unrest in the Niger Delta, the southern heartland of Africa's biggest oil and gas industry, where politicians armed thugs to intimidate voters.
But this year. it is the north which provides the biggest security headache. In two northern states, Kaduna and Bauchi, where some of the worst violence took place last week, voting will be delayed until Thursday.
"The north has become a killing field as a consequence of growing social, ethnic and religious intolerance," Abdullahi Adamu, a former state governor elected senator for Nasarawa West in the region, told the Daily Trust newspaper.
"Violence has drawn the north back several decades. We have murdered our brothers and sisters in cold blood, destroyed our property and even infrastructure and places of worship for no just cause," Adamu, a prominent member of Jonathan's party, said.
Some commentators have expressed shock that rioters attacked the palaces of emirs, traditional Muslim rulers, in a part of the country where their authority was once respected.
Properties of northern politicians and businessmen who backed Jonathan are also reported to have been attacked.
Nigeria, Africa's most populous country, with more than 150 million people, is split almost equally between a mainly Muslim north and a majority Christian south, although large minority groups live in both regions.
The series of elections began with a parliamentary vote which was delayed by administrative chaos, followed by the presidential ballot.
A successful conclusion of the elections, judged so far to have been the most credible since a return to democracy in 1999, could boost Nigeria's world standing and attract investment.