Nigeria's acting president Goodluck Jonathan was sworn in as head of state today following the death of president Umaru Yar'Adua.
He will next year lead the country to its most fiercely contested polls since its return to democracy more than a decade ago.
Mr Jonathan took the oath of office in front of government ministers, state governors and ambassadors at the presidential villa in Abuja almost 12 hours after Mr Yar'Adua died, aged 58, following a long battle with kidney and heart ailments.
Mr Jonathan had already been running Africa's most populous nation as acting president for several months while Yar'Adua was incapacitated.
"Nigeria has lost the jewel on its crown," Mr Jonathan said, announcing seven days of national mourning.
Mr Yar'Adua will be buried in his northern home town of Katsina tomorrow.
US president Barack Obama said his thoughts and prayers were with Mr Yar'Adua's family and remembered his "profound personal decency and integrity".
Mr Yar'Adua had been absent from the political scene since November, when he left for medical treatment for a heart condition in Saudi Arabia. He returned to Nigeria in February but remained too sick to govern.
Mr Jonathan assumed executive powers in February and has since consolidated his hold on power, appointing a new cabinet and his own team of advisers. But Mr Yar'Adua's death raises the stakes in the run-up to the next elections.
It is unclear if Mr Jonathan, who is from the southern Niger Delta, will run for president because of an unwritten agreement in the ruling party that power rotates between north and south.
The next four-year term is due to go to Mr Yar'Adua's Muslim north.
"The paramount issue will be who the new vice president will be. It'll probably be a northerner (who) will be front runner for the presidency in 2011," said Kayode Akindele, a director at Lagos-based consultancy Greengate Strategic Partners.
A presidential aide told Reuters there was no rush to swear in Mr Jonathan as head of state because, as acting president, he is already commander-in-chief.
Mr Yar'Adua, who pledged respect for the rule of law when he took office, initially was seen by many Nigerians as a breath of fresh air after eight years of former president Olusegun Obasanjo, an overbearing ex-military ruler with a penchant for disregarding court orders and legal detail.
He was Nigeria's first university-educated leader and won victory in April 2007 polls which, though marred by intimidation and ballot-stuffing, marked the first transfer of power from one civilian president to another since independence in 1960.
But the optimism quickly faded. Mr Yar'Adua earned the nickname "Baba Go-Slow", a reference to the local term for Nigeria's crippling traffic jams, for what critics said was slow progress on everything from economic reforms to restoring the shambolic energy sector.
His biggest achievement was in the restive Niger Delta, the heartland of Africa's biggest oil and gas industry.
Militant attacks rumbled on during the early part of his tenure, but his offer of amnesty last year led thousands of gunmen to lay down their weapons and has brought more than six months of relative peace in the region.
Reuters