A truck bomb aimed at the electoral commission headquarters ran into obstructions and failed to explode hours before the start of Nigeria's presidential vote on Saturday, the national police chief said.
The would-be attacker pointed the tanker truck -- loaded with fuel and gas cylinders rigged to explode --toward the building and placed a rock on the accelerator before jumping from the vehicle, said Police Inspector General Sunday Ehindero.
The tanker ran into obstructions and stopped before reaching the building in the capital, Abuja.
Ehindero called for calm only hours before polls were to open. "I'm calling on all Nigerians to go about their civil duties ... peacefully," Ehindero said.
He also said that militants who battled government forces for hours on the eve of the vote in a southern oil-rich state were seeking to kidnap the governor, who is also the ruling-party's vice presidential candidate.
Ehindero upped an earlier death toll in recent election violence, saying 34 police officers have died due to "criminal desperation that has attended the conduct of these elections" and that 40 civilians were killed.
He earlier said 21 died on April 14, the day of disputed state elections. Local media reported between 40 and 50 dead that day. He gave no specific time period.
A gunbattle raged for several hours Friday in Yenagoa, the capital of southern Bayelsa state. A top militant said fighters hoped to scuttle weekend presidential elections.
Goodluck Jonathan, the state governor and vice presidential candidate for the ruling People's Democratic Party, was scheduled to be in his home state to vote on Saturday. Ehindero said the gunmen sought to kidnap Jonathan.
After about two hours, the gunfire ended and the fighting appeared to subside.
Fighters of notorious gang leader Ateke Tom were hoping to scupper the vote, after widespread irregularities in state elections the week before, a top militant said requesting anonymity.
Elsewhere Friday, gunmen attacked a boat carrying workers to an oil rig in waters off Nigeria's unruly southern Niger Delta region, wounding six passengers, officials said.
Security forces drove off the attackers, a private security official said on condition of anonymity because of company prohibitions on dealing with the media.
Another security official, also speaking on condition of anonymity for the same reason, said three Nigerian workers initially feared kidnapped had been found hiding under the vessel's engine housing.
A military spokesman, Maj Sagir Musa, confirmed an attack had taken place, but had no details.
More than 150 foreigners have been kidnapped over the past year in the southern region where crude is pumped in Africa's largest producer.
Stepped-up violence has trimmed Nigeria's daily production by about one quarter, helping send global crude prices higher.