ABUJA, May 26 (AFP) - Nigeria, the world's most populous black nation, brings more than 15 years of military rule to a close Saturday when Olusegun Obasanjo is sworn in as the country's third elected president. The inauguration, to be attended by dozens of foreign representatives including Britain's Prince Charles and UN Secretary-General Kofi Annan, is being viewed around the world as a new chance for the country once seen as the powerhouse and hope of Africa. But the most populous country on the continent, home to one in five Africans, is now, after years of military regimes, viewed as dangerously fragile. And, for many, this is Nigeria's last chance too. A federation of 36 states, home to more than 108 million people, Nigeria is a diverse country, composed of more than 200 ethnic groups brought together by Britain in 1914. From the creeks and marshes of the southern delta region, to the deserts of the north, it is riven by differences in history, language, religion, tradition and wealth. The average income per head of population is 260 dollars per year. Yet Nigeria is the world's seventh largest crude oil producer, and boasts more dollar millionaires than any other African nation. Obasanjo, the man being sworn in as president, is a former general and was military ruler of the country from 1976 to 1979. Jailed under the late military ruler General Sani Abacha, he was released in June last year when Abacha died and was returned to power in elections in February, beating former finance minister Olu Falae. A leader of the centre-left Peoples Democratic Party (PDP), one of his first tasks will be to summon a government from among members of the new 109-member Senate and 360-member House of Representatives. Obasanjo and his new government will then have to get down quickly to tackling some of the massive problems left behind by the succession of military regimes which have misruled Nigeria for all but four years since a first coup in 1966. Among them are the tensions in the under-developed oil-producing delta region, the stagnant condition of the economy, the demands for devolution to the regions, the collapse of infrastructure and the corrosive spread of corruption in government. Coming into office, Obasanjo will find foreign reserves depleted, a government deficit higher than previously thought, and face strikes in the banking and education sectors. His advisers will have already told him about the general economic problems, and need for spending in health and education. According to political analysts here, failure to resolve some of the problems could see a renewal in the pressures for a break up of the country, particularly in the restive southwest, and a collapse in law and order. According to pro-democracy campaigners here, the return of elected government, however, does give Nigeria a chance, its first since the military ousted the previous, short-lived civilian governments in 1966 and 1983. "We haven't previously allowed civilian, democratic rule, a chance. We have to learn to weather a storm as a democracy and entrench democratic rule," said Clement Nwankwo, head of a coalition of 63 democracy and human rights groups. "An elected government has to listen more and react more to the problems everyone knows there are in Nigeria. This is an elected government and that is why it is a new chance."  