|The Red Cross said 'many people' had been killed in the states of Kano and Kaduna but gave no exact details [AFP]
At least six people have been killed and hundreds of others injured in rioting following the election victory of Goodluck Jonathan, the incumbent president.
Soldiers patrolled the streets of cities in Nigeria's mainly Muslim north on Tuesday as aid workers began to assess the toll.
The Red Cross said that hundreds of people had been injured and thousands of people displaced as a result of the protests.
Six burned corpses were seen on the outskirts of the state of Kaduna, while burned out minibuses and cars lined the roads, according to an Associated Press report.
Al Jazeera's Yvonne Ndege, reporting from the capital Abuja, said the states of Kaduna and Kanu had been particularly hit by post-election rioting and that "eyewitness accounts [are] flooding in from people saying they're under attack".
"We're hearing churches have been set on fire; chaos and violence is unfolding in many villages and people are running for their lives," she said.
"It is a huge concern and it is really casting a very negative shadow on elections which have been declared free and fair by observers."
Umar Abdul Mairiga, the Nigeria Red Cross disaster management co-ordinator, said: "The displaced people are getting hostile because nothing is coming up in terms of relief."
Also on Tuesday, Jonathan suspended Emmanuel Iheanacho, his interior minister, handing over his portfolio to the minster for labour.
A statement from the president's office said that Iheanacho had been suspended "as a result of a number of lapses in the political leadership of the ministry traceable to his personal and official conduct".
The statement did not say whether the move was connected to the post-election violence.
Jonathan, who heads the Peoples Democratic Party (PDP), won Saturday's presidential election, defeating Muhammadu Buhari, a former military leader from the country's north, in a poll that some have said was flawed.
Despite those allegations, international observers described the poll as the fairest Nigeria has held in decades.
John Kufuor, a former president of Ghana and the lead election observer from the African Union, told Al Jazeera that he was "taken aback" by reports of violence as he had observed the elections take place "credibly, peacefully and transparently".
But hours before Jonathan was declared the winner on Monday, Buhari, who stood on the platform of the Congress for Progressive Change (CPC), told Al Jazeera he believed the election had been systemically rigged.
"We have evidence in our hands that the computers [used in the voting process], were programmed to produce rigged results," he said.
Jonathan called for calm in a televised address to the nation late on Monday, urging Nigerians to "quickly move away from partisan battlegrounds and find a national common ground".