Nigerian President Yar'Adua dies after long illness
Umaru Yar'Adua's death is announced on state TV
Nigerian President Umaru Yar'Adua has died at his presidential villa following a long illness.
The government announced seven days of national mourning and said the president would be buried on Thursday.
Vice-President Goodluck Jonathan has been sworn in as head of state in a ceremony in the capital Abuja.
Mr Yar'Adua, 58, came to power in 2007 promising many reforms. Analysts say he made the most progress in tackling unrest in the oil-rich Niger Delta.
Nigerian TV interrupted normal programming to announce the news in a brief statement early on Thursday.
Martin Plaut, BBC World Service Africa editor
The uncertainty at the heart of Nigeria has been tremendously destabilising.
There has been considerable unrest in the central state of Jos recently with clashes between Muslims and Christians, and people put this down partly at least to the fact that there was not a firm hand at the centre of power.
Goodluck Jonathan is already exercising control. He will take over.
But this does cause difficulties because there is a convention that this was the turn of the Nigerian Muslims from the north to control Nigeria and Goodluck Jonathan is from the south.
He will be taking over during the turn of the Nigerian northerners, the Muslims, to control Nigeria.
The announcer said: "The president and commander-in-chief of the armed forces, Umaru Musa Yar'Adua, died a few hours ago at the presidential villa.
"Security aides notified the national security adviser, General Anou Bissou, who immediately called the acting president. The late president has been ill for some time."
Government spokesman Olusegun Adeniyi said President Yar'Adua died with his wife, Turai, at his side.
Shortly after Mr Yar'Adua's death was announced, people began arriving at the presidential villa in the capital Abuja to pay their condolences.
Mr Yar'Adua will be buried in a Muslim ceremony later on Thursday in his home state of Katsina, in the north of the country.
A spokesman for Mr Jonathan said the acting president had received the news with "shock and sadness".
"Nigeria has lost the jewel on its crown and even the heavens mourn with our nation tonight," Mr Jonathan said in a statement.
He declared Thursday a holiday as part of the seven days of mourning.
Reports said Mr Yar'Adua died between 2100 (2000 GMT) and 2200 (2100 GMT) on Wednesday in Abuja.
US President Barack Obama led tributes from world leaders.
Mr Obama praised "President Yar'Adua's profound personal decency and integrity, his deep commitment to public service, and his passionate belief in the vast potential and bright future of Nigeria's 150 million people".
Born in northern Katsina state in 1951
University chemistry professor before entering politics
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