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Susan Walsh, Pool, Associated Press
U.S. Secretary of State John Kerry, center, is escorted by U.S. Ambassador to Nigeria James F. Entwistle, second right, upon his arrival at Nnamdi Azikiwe International Airport in Abuja, Nigeria Friday, May 29, 2015. Kerry is attending the inauguration of Muhammadu Buhari as President of Nigeria.

ABUJA, Nigeria — Nigerians celebrated their newly reinforced democracy Friday, dancing and singing songs and praises at the inauguration of Muhammadu Buhari, the first candidate to beat a sitting president at the polls.

As Buhari finished taking the oath of office in traditional robes and an embroidered cap, the crowd at Eagle Square in Nigeria's capital roared its approval. The former general then inspected troops in the plaza, decked out in colors of Nigeria's green and white flag, from the back of an open vehicle and waved at supporters.

A 21-gun salute boomed over Eagle Square during the handover of power which is a turning point in Nigeria's democratic evolution. Security was tight. In 2010, two car bombs and a grenade blast triggered by militants from Nigeria's oil patch killed 12 people at Independence Day celebrations.

Buhari has a wealth of international goodwill. A phalanx of African leaders attended the inauguration along with France's Foreign Minister Laurent Fabius and U.S. Secretary of State John Kerry, looking to mend fences broken under the discredited administration of Goodluck Jonathan.

Some nervous politicians fear Buhari's promise to retrieve ill-gotten gains for coffers emptied by massive corruption. Nigerian newspapers carried unconfirmed reports that some politicians already have returned millions of dollars in hopes of avoiding scrutiny.

"We see him as our only hope against this crippling corruption," said Efo Okorare, curator of an open-air exhibition of Nigerian leaders, pointing out the many in military uniforms. Buhari ruled briefly as a military dictator in the 1980s. The 72-year-old says that as a "born-again democrat" he can heal the woes of Africa's biggest nation, economy and oil producer.

Buhari inherits leadership of a nation plagued by an Islamic uprising has killed more than 13,000 people driven more than 1.5 million people from their homes. Nigeria is also $63 billion in debt and is borrowing to pay government workers.

Jonathan allowed the nearly 6-year-old Islamic insurgency to flourish before agreeing to an international offensive with troops from neighboring countries this year. His perceived indifference to the suffering caused by the uprising also hurt him. Presidents of neighboring countries have complained of lack of cooperation from Nigeria's government and military in the offensive against Boko Haram, the Nigerian Islamic extremist group.

Buhari, a Muslim from the north, was first installed as president after a military coup on New Year's Eve 1983. In August 1985, he was himself deposed because his fight against corruption and the life-long jail terms for politicians found guilty by military tribunals proved too draconian even for the coup plotters, who felt threatened.

Political science professor Richard Joseph of Northwestern University said Buhari's victory has hopeful international implications.

"The world desperately needs a victory against cultist jihadism. Nigeria (under Buhari) can provide it," he said.