ABUJA - Nigeria's new leader, Goodluck Jonathan, vowed yesterday that electoral reform and fighting graft would be top priorities as he steers the nation to its most fiercely contested polls since the end of military rule.

Jonathan was sworn in following the death on Wednesday of President Umaru Yar'Adua, 58, after a long battle with kidney and heart ailments.

"Our total commitment to good governance, electoral reform and the fight against corruption would be pursued with greater vigour," Jonathan said after taking the oath of office in Abuja.

Maintaining peace in the Niger Delta would also be a top priority, he said after being sworn in by Chief Justice Aloysius Katsina-Alu.

Jonathan has been acting president for several months and few expect any policy changes.

Yar'Adua had been absent from the political scene since November, when he left for treatment for a heart condition in Saudi Arabia. He returned to Nigeria in February but was too sick to govern and never made another public appearance.

Jonathan assumed executive powers three months ago and has since appointed a new cabinet and his own team of advisers. He will now appoint a vice-president and the pair will complete the unexpired presidential term until the elections due in April next year.

His choice of vice-president could determine the outcome of those polls.

It is unclear if Jonathan, who is from the southern Niger Delta, will run for president because of an unwritten agreement in the ruling party that power should rotate between north and south.

The next four-year term is due to go to Yar'Adua's Muslim north.

"The main issue will be who will be the vice-president. It'll probably be a northerner (who) will be the frontrunner for the presidency in 2011," said Kayode Akindele of Greengate Strategic Partners.

Yar'Adua was to be buried in Katsina yesterday. US President Barack Obama praised his "profound personal decency and integrity".

Yar'Adua, who won the polls in April 2007, was initially seen by many Nigerians as a breath of fresh air after eight years of ex-president Olusegun Obasanjo, an overbearing ex-military ruler who disregarded court orders and legal detail.

But the optimism quickly faded as critics slammed him for slow progress on everything from economic reforms to restoring the shambolic energy sector. - Reuters