Goodluck Jonathan has been sworn in as president of Nigeria for a four-year term.
Foreign heads of state attended a lavish ceremony, which began with a military parade and inspection at Eagle Square in the capital, Abuja, on Sunday.
Mr Jonathan was promoted from vice-president after Umaru Yar'Adua died in office in 2010.
Despite his win by a clear margin, the BBC reports Nigeria still has serious divisions. There were deadly riots after last month's polling.
"Together we will unite our nation, improve the living standards of all our people, whether in the north or in the south, in the east or in the west,'' he said after taking the oath of office.
Mr Jonathan, 53, won nearly 60% of the vote. He is a southern Christian whose leading challenger was from the north, which is mainly Muslim.
