Sudan's President Omar al-Bashir has been declared the winner of this month's landmark elections, despite facing war crimes charges over Darfur.
Former rebel leader Salva Kiir has been confirmed in power in the semi-autonomous south in the first polls since the north-south war ended.
The polls were one of the world's most complex ever and Sudan's first multi-party elections in 24 years.
Observers and opposition parties have complained of fraud in north and south.
Tension was raised over the weekend, with reports of clashes along the north-south border.
Some 55 people were said to have been killed in clashes between an Arab community and southern soldiers.
The BBC's James Copnall in Khartoum says President Bashir's re-election could be interpreted as a popular rebuke for the International Criminal Court, which has issued an arrest warrant against him for war crimes in Darfur.
Sudan's leader strongly denies the charges.
His two main challengers withdrew before the elections began, claiming that the process had already been rigged.
Our correspondent says these accusations and withdrawals have dented the credibility of the elections.
The EU and the Carter Centre said the polls were below international standards.
But former US President Jimmy Carter said he believed the international community would recognise the winners all the same
Mr Bashir and his National Congress Party were already well ahead in the results already announced from the 11-15 April elections.
As well as the national and southern presidential contests, elections were also held for the national, regional and state parliaments and state governors.
The weekend violence was the most serious since the polls.
The clashes reportedly began over grazing rights for cattle - a common source of conflict in the area.
But southern government officials say their soldiers were attacked by members of the northern army - charges denied in Khartoum.
The SPLM joined a national coalition government after a 2005 peace deal but relations remain tricky between the supposed partners.
A referendum is due in 2011 on whether the south, where most people are Christian or follow traditional religions, should secede from the Arab-dominated mostly-Muslim north.
Mr Bashir has said he would respect the outcome of the referendum but some fear conflict could resume, especially in the oil-rich border region.