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The incumbant has declared defeat in the hotly contested race, sources say. Buhari previously helmed the country under military rule from 1983 - 1985. He won by two million votes.

Young men dance in front of a makeshift figure of former military ruler and presidential candidate Muhammadu Buhari in Kaduna, which was hit hard by interreligious violence during the 2011 election, on March 29, 2015.

Muhammadu Buhari reportedly leading incumbent President Goodluck Jonathan by 2 million votes.

The Hungarian (L) and Mexican (R) Foreign Ministers in Mexico City, March 26, 2015. RONALDO SCHEMIDT/AFP/Getty Images

Hungarian trading houses are opened in Mexico City and Santiago, Chile, as exports increase.

A relative of dead Bangladeshi blogger Washiqur Rahman reacts after seeing his body at Dhaka Medical College in Dhaka on March 30, 2015, after he was killed in an attack in the Bangladeshi capital.

Atheist blogger hacked to death one month after similar attack. 

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Turkish Airlines flights made two unexpected landings.

 A boy is seen next to a tank as armed members of Yemen's General People's Committee stand guard at the entrance of the city of Aden in Yemen as part of the precautions taken against Houthis on March 29, 2015.

Clashes continue with Iranian-allied Houthi fighters in Aden.

The seals of the U.S. Cyber Command, the National Secrity Agency and the Central Security Service greet employees and visitors at the campus the three organizations share March 13, 2015 in Fort Meade, Maryland.

Two suspects attempted to ram vehicle through gates of agency's HQ.