Nigeria is to hold seven days of mourning for President Umaru Yar'Adua, who died on Wednesday.
Mr Yar'Adua, 58, who became president in 2007, had been ill for some time and had not been seen in public for months.
In November, Mr Yar'Adua went to a hospital in Jeddah, Saudi Arabia, for several months. A presidential spokesman said at the time that he was being treated for acute pericarditis, an inflammation of the lining around the heart.
His long absence and the lack of detailed information about his health led to a political limbo in Nigeria that was only filled when Vice-President Goodluck Jonathan was named acting president, after much wrangling, in February.
Mr Yar'Adua returned to Nigeria later in February, but Mr Jonathan remained as acting president, the BBC reports.
Reports say he will now be sworn in as president.