Nigerians are waiting in hope and fear for results of the most tightly contested presidential election in the nation's turbulent history. Collation of results starts at noon (1100 GMT). Results are expected later Monday.

One radio station played the song written by entertainment star 2Face Idibia: "Vote not fight; Election no be war!"

In relative peace, millions voted on Saturday and tens of thousands Sunday despite technical glitches, deadly attacks on northeastern polling stations by Islamic extremists and political thuggery in the south.

Fears center on violence erupting once results are announced in the high-stakes contest to govern Africa's most populous and richest nation. President Goodluck Jonathan is challenged by former military dictator Muhammadu Buhari. More than 1,000 people died in northern riots after Buhari lost to Jonathan in 2011.