Reporting from Johannesburg, South Africa -- Nigeria buried its president on Thursday and swore in his successor, Goodluck Jonathan, amid fears of a debilitating power struggle in the ruling party.

Politicians hailed the smooth power transfer, but the death of President Umaru Yar'Adua on Wednesday night after a five-month illness could lead to infighting between northerners and southerners in the ruling People's Democratic Party should Jonathan, a southerner, decide to run for the presidency in elections due next year.

Jonathan's candidacy would shatter an unwritten deal in the PDP that rotates the presidency for eight years to a leader from the mainly Christian south and eight years to someone from the mainly Muslim north. The rotation is seen as vital to Nigeria's political stability.

The arrangement, known as the "zoning" policy, was recently affirmed by the party and means an Islamic candidate should run as the PDP candidate because Yar'Adua, a Muslim, served less than four years.

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