Nigerians are voting Saturday in historic presidential elections, amid violence and delays in distributing ballots.
The vote marks the first peaceful transfer of civilian power since Nigeria gained independence from Britain in 1960.
The elections have been plagued by violence that has killed dozens of people across Nigeria. An attempted attack on the election commission headquarters in the capital of Abuja early Saturday failed when a gas tanker truck rigged to explode stopped short of its target. The truck did not explode.
Former U.S. Secretary of State Madeleine Albright and former Canadian Prime Minister Joe Clark are among election observers monitoring the vote.
Saturday's vote was delayed by two hours because election officials needed more time to distribute newly printed ballots to include Vice President Atiku Abubakar. Nigeria's Supreme Court earlier this week overruled a decision by the election commission to disqualify Abubakar from the race.
Heavy gunfire broke out late Friday in many parts of the capital of Bayelsa state (Yenagoa), including at a hotel where the ruling party's vice presidential candidate, Goodluck Jonathan, is staying. His aides say he was not harmed.
Militants in the state say they are angry at alleged fraud that took place during last Saturday's state elections. Authorities also say a military helicopter involved in operations against the militants crashed Friday night, killing three crew members.
In a nationally broadcast speech Friday, Nigerian President Olusegun Obasanjo asked for patience with his country's voting system. He conceded the system is "flawed," but asked election observers to understand Nigeria's limitations as a developing nation and fledgling democracy.
Mr. Obasanjo is due to step down next month after serving two four-year terms.
Some information for this report was provided by AP and Reuters.