An attempt to blow up the electoral headquarters with a petrol tanker, attacks by thugs, missing ballot papers and low turnout undermined Nigeria's presidential election today.
The vote should seal the first handover from one civilian president to another in Africa's most populous nation, scarred by three decades of corrupt military rule, and has been seen as a possible democratic beacon for the continent.
But opposition parties said there were many problems with ballots, voting began late or not at all in some places and political thugs stole ballot boxes.
Hundreds of youths wielding sticks smashed cars and set fire to roadside shacks in Daura, the northern home town of leading opposition candidate, Muhammadu Buhari, after his supporters reported thousands of ballots missing.
The crowd dispersed after Buhari called for a peaceful vote.
Opposition parties accused the ruling People's Democratic Party (PDP) of removing ballots from secure compounds operated by the Independent National Electoral Commission (INEC) and marking them up illegally.
"What has happened right now across the country has shown the PDP, the government, INEC and some of the law enforcement agencies are not prepared to have a free and fair election," Buhari said.
Local media reported little or no voting in the southeastern states of Enugu and Anambra, where people said they were disenfranchised.
Thugs in Kano armed with swords and guns stole ballot boxes, while an election official in southwestern Ondo state was abducted by a gang dressed in police and army uniforms.
Hours before polling stations opened, unknown attackers tried to blow up the national electoral headquarters in the capital Abuja with a fully laden petrol tanker. It hit a telephone pole outside the building and did not explode.
Electoral commissioner Maurice Iwu blamed "desperate Nigerians" out to sabotage democracy, but said polls must go on.