* Incumbent Jonathan seen as favourite, faces divided opposition
* Graft, violence are twin blights of Africa’s top oil producer
* Election politics seen stoking ethnic, religious tensions (Recasts, adds details, quotes, background)
ABUJA, Nov 11 (Reuters) - President Goodluck Jonathan promised Nigerians on Tuesday he would fight corruption and defeat the Islamist Boko Haram insurgency as he announced his bid to win a second term at the head of Africa’s biggest economy in a February election.
A southern Christian president heading Africa’s top oil producer, Jonathan is seen as a strong incumbent despite a raft of multi-billion-dollar oil scandals and his government’s inability so far to end the five-year-old insurgency waged by Boko Haram, mostly in the Muslim north.
“After listening to the clarion call of Nigerians, I have accepted to present myself to serve a second term,” Jonathan told cheering supporters at a rally in the capital, Abuja.
His widely expected announcement was a formality after he had already picked up nomination papers from his ruling People’s Democratic Party (PDP) last month, signalling his intent to run.
Jonathan is seen as favourite because elections in the oil-dependent nation are fought more on the basis of political patronage than on policy. He will also be helped by a divided opposition which is still to chose his main challenger.
But he faces fierce criticism at home and abroad for failing to rein in corruption and guarantee security for all Nigerians.
Jonathan’s announcement came a day after a suspected Boko Haram suicide bomber attacked a school in the northeast town of Potiskum, killing at least 48 people.
The president said Boko Haram, which has announced the creation of an Islamic caliphate after capturing territory in the remote northeast, had cast a dark cloud over the country.
A ceasefire with the group unilaterally announced by his government last month has failed to stop almost daily attacks, which have included the mid-April abduction by Boko Haram of more than 200 schoolgirls from a northeastern town.
“We will surely get our daughters freed and defeat terror in our country,” Jonathan said.
Despite pledges of help from the United States, Britain, France and Israel in the war against Boko Haram, there are fears that violence will increase in the run-up to the February vote as political tensions heighten ethnic and religious differences.
Jonathan’s government has also come under pressure to prop up the local naira currency which has fallen over 6 percent this year due to a decline in oil prices for the crude exports on which the country depends.
The sharp drop in global oil prices has raised the twin spectres of a potential currency devaluation and budget shortfalls but analysts have said it is unlikely the currency will be devalued before the election.
Jonathan’s administration has also faced accusations of not doing enough to stamp out endemic corruption, including billions of dollars of oil revenues that have been reported missing.
“Corruption is one of the major stains in our country,” Jonathan said, promising to prosecute corrupt officials.
In the ranks of the main opposition All Progressives Congress, the top contenders for the presidential ticket next year are former military ruler Muhammadu Buhari and recently defected vice president Atiku Abubakar, both Muslim northerners.
In 2011, Buhari’s defeat at the hands of Jonathan triggered three days of bloodshed that left 800 dead and 65,000 displaced. (Additional reporting and writing by Bate Felix in Lagos; Editing by Pascal Fletcher and Giles Elgood)
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