An election for governor of Anambra state in Nigeria's oil-rich Delta region has been condemned amid reports of vote-buying and ballot-box theft.
Peter Obi was re-elected but just 300,000 people cast their ballots from an electorate of 1.8 million.
Gangs of youths intimidated and harassed voters and snatched three ballot boxes from polling stations.
The chaos has dampened hopes of improvements to Nigeria's voting system ahead of national elections in 2011.
President Umaru Yar'Adua had promised to sort out Nigeria's notoriously corrupt elections after he was elected in a widely-criticised poll in 2007.
Mr Obi had initially refused to vote because he discovered he was the only member of his family whose name appeared on the electoral roll. He later changed his mind.
Chukwuma Soludo, who came third in the poll, complained of "brazen manipulation".
"Let me use this opportunity to congratulate my friend Mr Peter Obi," said Mr Soludo.
"In spite of the grave flaws, INEC [Independent National Electoral Commission] has declared you winner of the election."
The BBC's Fidelis Mbah in Anambra says he witnessed three ballot boxes being stolen by gangs of youths - at least one of whom was armed and dressed in police uniform.
He says one polling station had 500 registered voters but just three people could find their names on the list.
Although the manipulation appeared to be politically motivated, our correspondent says it is not clear who was responsible.
Many polling stations opened hours late and there were confrontations as voters discovered their names were not on the electoral register.
