Profile: President Umaru Yar'Adua

President Umaru Musa Yar'Adua is the first civilian leader in Nigeria to have taken over from another after winning controversial polls in April.

The former chemistry teacher is also the first Nigerian leader for 40 years to be university educated, but little is known about him - even in his home state.

The reclusive Muslim governor comes from the northern state of Katsina and is not a major political mover or shaker.

But at 56, he boasts a political pedigree that dates back to the 1960s when his father was appointed as a minister in the post-independence administration.

His late elder brother who was an army general served as Olusegun Obasanjo's deputy when the former president was Nigeria's military ruler during the 1970s.

They were both imprisoned together after they were accused of plotting a coup against late military strongman Gen Sani Abacha.

Backing

Mr Yar'Adua's emergence as the ruling People's Democratic Party's candidate in the presidential election in April 2007 rests almost exclusively on the support of Mr Obasanjo.

Nigerian presidency sources say Mr Obasanjo used a mixture of inducements and threats of investigation by the anti-graft agency to persuade 10 influential state governors to withdraw from the race and back Mr Yar'Adua.

Analysts say that by backing Mr Yar'Adua to succeed him, Mr Obasanjo will hope to continue pulling strings now that he has stepped down as president.

Shortly after he won his party's nomination, Mr Yar'Adua paid tribute to former President Obasanjo whom he described as "the father of democracy and good governance in Nigeria".

He pledged to continue with Mr Obasanjo's economic reforms and fight against corruption.

Independence

But analysts say that Mr Obasanjo might have difficulty trying to control Mr Yar'Adua who is said to be quite independent-minded.

"He differed with his own brother on many occasions and criticised him on many issues and so I don't expect him to be easily controlled by Obasanjo," says the BBC's Mansur Liman in Abuja.

Although he is reputed to be prudent in managing funds in Katsina State where he had been governor for the past seven years, critics say contracts have gone to companies with links to his family's vast businesses.

He was among only a few Nigerian governors that publicly declared their assets before he was sworn-in as governor in 1999 and in 2003 - when he won a second term. He is also one of the few serving governors not being investigated for corruption.

As an undergraduate student in Nigeria's Ahmadu Bello University, Mr Yar'Adua was a self-confessed Marxist and criticised his elder brother's 'capitalist' leanings.

A man of few airs and graces, he is also known to have ignored the advice of aides and bodyguards to walk alone to tobacco kiosks to buy a single cigarette.

Described by his critics as taciturn and not known for his tolerance of opposition, Mr Yar'Adua has sometimes been underestimated.

As one commentator put it, "because he's quiet, people mistake him for a weakling. But he's someone who knows his own mind".

After his controversial election, Nigeria's new president will need all these skills to lead one of the continent's most testing countries.