The re-election of Goodluck Jonathan as president of Nigeria has led to dozens of killings and thousands of people leaving their homes, according to the Red Cross.
Riots erupted in the northern provinces of Kano and Kaduna after Jonathan, a southerner, was declared winner of the poll. Most of the homeless are also in the north, although people in the southern province of Anambra have also fled their homes in fear of attacks.
According to reports, more than 200 people have died in post-election violence while security forces have arrested hundreds of people.
A reporter for Al Jazeera said: What we're hearing is that the violence is taking a new dimension. Eyewitnesses are telling us that soldiers - or men dressed in military fatigues - are conducting door-to-door searches, removing people from their homes and actually attacking and in some cases killing them.
Both Jonathan and General Muhammadu Buhari, who lost his bid for the presidency, have made appeals to the public for calm.
The election results have shown the stark sectarian differences in vast, oil-rich Nigeria.
Buhari, a Muslim and a northerner, was supported by the entire northern regions of the country, while Jonathan, a southerner and a Christian, won almost all of the south.
Buhari told the Voice of America radio service that his party, the Congress for Progressive Change, noticed “irregularities” during voting in the southern parts of the country.
I urge people to calm down and be law-abiding as we are pursuing these irregularities with [the electoral commission] with a view to ensure justice for them, he said.
However, international observers sent to Nigeria to monitor the election determined they were free and fair.
It is regrettable that when the international observers are commending us for credible elections, we witness violence in some parts of the country, it is really regrettable because it is uncalled for, Jonathan said.
A correspondent for BBC based in Nigeria wrote: “Most of those behind the rioting have been unemployed young men - uneducated and deprived. Often they are only remembered by politicians at elections, when they are sometimes paid to do their bidding. They could send any conflict out of control, because it provides them with an opportunity to loot and attack the people they perceive as their enemies.”
He added: “Irrespective of political party and region, 12 years of civilian rule have brought little change to the lives of Nigerians. But the north is far behind the south in terms of development, education and the availability of economic opportunities. Good governance, not political platitudes from the elite, is what many say is needed for the future.”