Nigeria election results due to start trickling in

Election officials count ballot papers at the end of voting in one of the polling stations in Yola, Nigeria

Results from Nigeria's elections, potentially the closest contest since the end of military rule in 1999, were due to start trickling in on Monday after a weekend vote marred by confusion, arguments and sporadic violence.

The election pits President Goodluck Jonathan against former military ruler Muhammadu Buhari for the favour of an electorate divided along a complex mix of ethnic, regional and in some cases religious lines in Africa's most populous nation.