Twenty years ago he was a military ruler handing over power to a civilian government.

This time he is the civilian president receiving the reins of power from the miltary.

General Obasanjo speaking in June 1998

An ethnic Yoruba from southwest Nigeria, he enjoys the backing of many in the Hausa-speaking north which has dominated Nigerian government for decades.

He also has the key support of many retired and serving military officers.

Now 61, he first gained renown as the soldier who took the surrender of Biafran forces in the 1967-70 civil war.

He took power in 1976 when Brigadier Murtala Ramat Muhammed was assassinated.

International acclaim

He received international acclaim in 1979 for being the first modern African military leader to transfer power to civilians voluntarily.

Nigerians voted for a new national assembly and Alhaji Shehu Shagari, of the National Party of Nigeria, was elected president, and a civilian government took office.

Mr Obasanjo then said he had retired from politics. He returned to his home state where he set up a poultry and pig farm. But he also continued to sit on a number of international committees dealing with African problems, and set up his own African Leadership Forum.

He became increasingly critical of subsequent Nigerian military regimes, and was jailed by the late military dictator General Sani Abacha in 1995 on charges of plotting a coup along with 43 other soldiers and civilians.

Released

When General Abdulsalam Abubakar took over as head of state following the unexpected death of General Sani Abacha, he released nine key political prisoners, including Mr Obasanjo in June 1998.

An exclusive interview with General Obasanjo in June 1998

In a BBC interview shortly after his release from prison he said he thought moral standards in Nigeria had dropped, and that very few Nigerians still stood for their principles.

He said that too many Nigerians tried to rationalise their support for General Abacha - who led the country into international political isolation - because they believed they could influence him. "Now who can tell you that he can reform the devil?" he asked.

He initially said he would not run for the country's top office but in November last year announced he had changed his mind after consultations with friends and supporters.

General Obasanjo said his nomination as PDP party leader ended what he called the illogical polarisation of society between soldiers and civilians.

But although he spent three years in jail under General Abacha, after being accused of a coup plot, he's still widely seen as the favoured candidate of the military.

Critics accuse him of being too close to the generals and ex-generals who've ruled Nigeria for the past fifteen years.