"No political ambition can justify violence or the shedding of the blood of our people," Jonathan, who is running for re-election, said Friday in a televised broadcast.
In a country steeped in a history of coups, bloodshed caused by politics, ethnicity, land disputes and, lately, the Boko Haram Islamic uprising, the election is important as Africa's most populous nation consolidates its democracy.
Nigeria's political landscape was transformed when the main opposition parties formed a coalition two years ago and for the first time united behind one candidate, former military dictator Muhammadu Buhari who is Jonathan's main challenger.
The election is only the eighth since independence from Britain in 1960 and the first ever to raise the possibility of a democratic transfer of power through the ballot box, a high-stakes contest in Africa's biggest oil producer where patronage and corruption are rife. No incumbent has ever lost an election.
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His state-sponsored but independent organization reported at least 58 killings by Feb. 13 and there have been many more since then, Odinkalu told AP. He also complained that politicians have done little to dampen tensions.
Meanwhile, Nigeria's military announced it had destroyed the headquarters of Boko Haram's so-called Islamic caliphate, in the northeastern town of Gwoza, in fighting Friday that left several extremists dead.