World leaders back Ouattara as Ivory Coast poll winner
World leaders have voiced their support for Ivory Coast opposition candidate Alassane Ouattara, saying he is the true winner of a presidential run-off.
Initial results giving Mr Ouattara victory were overturned by officials, who declared President Laurent Gbagbo winner. He is now due to be sworn in.
Prime Minister Guillaume Soro tendered his resignation, backing Mr Ouattara.
Mr Ouattara is also expected to be sworn in at a rival ceremony held in a compound guarded by UN peacekeepers.
The US, UN and France - the former colonial power - have urged Mr Gbagbo to accept defeat.
Sunday's presidential run-off was intended to reunify the world's largest cocoa producer after a civil war in 2002, but now could leave the nation with two rival presidents.
On Saturday, Mr Soro, a former rebel leader, offered Mr Ouattara the resignation of the government.
Mr Soro had earlier warned that overturning the results threatened to derail attempts to stabilise and reunify the country after the war.
On Thursday, the Independent Electoral Commission (IEC) declared that Mr Ouattara had won the 28 November run-off by 54.1% to 45.9%.
But after Mr Gbagbo and his supporters alleged the ballot had been fraudulent, the Constitutional Council overruled the Commission.
Chairman Paul Yao N'Dre said Mr Gbagbo had secured just over 51% of the vote.
Ivorian state media said Mr Gbagbo would be sworn in at a midday ceremony on Saturday.
'Held to account'
US President Barack Obama has rejected the Constitutional Council's decision.
"Independent Electoral Commission, credible and accredited observers and the United Nations have all confirmed this result and attested to its credibility," he said.
He congratulated Mr Ouattara and said the international community would "hold those who act to thwart the democratic process and the will of the electorate accountable for their actions".
French President Nicolas Sarkozy told Mr Gbagbo to "respect the will of the people, abstain from any action that might provoke violence" and to help establish peace.
UN Secretary-General Ban Ki-moon earlier called on Mr Gbagbo "to do his part for the good of the country and to co-operate in a smooth political transition".
Nigerian President Goodluck Jonathan, who is current chairman of regional bloc Ecowas, said all parties should "respect and fully implement the verdict of the Ivorian people as declared by the Independent Electoral Commission".
The head of the UN mission in Ivory Coast also said it regarded Mr Ouattara as the winner, while the African Union said it was "deeply concerned" by the developments.
The head of the International Monetary Fund, Dominique Strauss-Kahn, said the IMF would only work with an Ivory Coast government recognised by the UN.
Mr Ouattara told reporters on Friday evening: "I am the elected president of the Republic of Ivory Coast.
"The Constitutional Council has abused its authority, the whole world knows it, and I am sorry for my country's image."
There have been dramatic scenes since Sunday over the declaration of the results.
On Tuesday, Mr Gbagbo's representative in the IEC tore up the first batch of results as the commission's spokesman was about to announce them.
The IEC head, Youssouf Bakayok, then went ahead with an announcement on Thursday, speaking under armed guard at a hotel rather than from the commission's headquarters, declaring Mr Ouattara the winner with 54% of ballots cast.
Not long afterwards, Mr N'Dre said that, as the announcement had come after Wednesday's legal deadline, those results were "null and void".
The two candidates represent the two sides of the north-south divide that exists religiously, culturally and administratively, with the northern half still controlled in part by the former rebels.
The BBC's John James in Abidjan, the country's main city, says the Constitutional Council's decision has come as a shock to many - especially the opposition.
Youths from the opposing camps took to the streets in Abidjan and other towns, throwing stones and burning tyres.
The military has closed the borders and international news sources are suspended. An overnight curfew is in place.
Both the army and UN peacekeepers have been patrolling the streets of Abidjan since Sunday.
At least four people have been killed in election-related clashes in Abidjan this week.