MAIDUGURI, Nigeria (Reuters) - A bomb blast struck a police chief's convoy in eastern Nigeria on Monday, killing 11 people, a witness and an official said, a day after attacks in other areas killed at least 19.
No group immediately claimed responsibility for the bombing in the town of Jalingo but Islamist sect Boko Haram, which wants to carve an Islamic state out of Nigeria, has been blamed for many such previous attacks.
A string of bombings and shootings in the last five days has dampened hopes that arrests and killings of Boko Haram members by the military in recent weeks had stemmed its ability to carry out large-scale attacks in Africa's largest oil producer.
Jalingo is the capital of Taraba state, which borders Cameroon and had previously been spared the insurgency plaguing Nigeria's north.
"At least 11 people were killed and 22 people injured near police state headquarters Jalingo at 0830 (0730 GMT) when the police commissioner was on his way to office," said Ahmed Bello, a local Nigeria Red Cross official.
He said the blast happened between the state government finance office and the police headquarters.
Abubakar Moyoyo, a Jalingo businessman, told Reuters by phone he had seen 11 dead bodies at the scene.
The police commissioner, Mamman Sule, said his team were investigating whether he was the target of the attack. He confirmed three deaths and said the windscreen of his car had been shattered by the blast.
Nigerian police are often cautious over death tolls until official figures are agreed with senior officers in Abuja.
In the past year, Boko Haram has tried to extend its reach beyond its north-eastern heartland, mounting attacks in and around the capital Abuja. The Jalingo strike followed two attacks on Christian worshippers in other parts of the country on Sunday that killed at least 19 people.
Gunmen attacked a university theatre being used for Christian services in the northern city of Kano and a church in northeast Maiduguri, Boko Haram's hometown.
The sect's attacks have usually been on police and government in the mostly Muslim north, but it has also increasingly struck Christian worshippers in the past few months.
President Goodluck Jonathan has been criticised for failing to tackle the violence, which has gained momentum since his presidential election victory a year ago.
He has relied mostly on a tough military approach, with mixed results. A brief attempt at mediated dialogue with Boko Haram broke off last month within days.
Suicide car bombers targeted the offices of newspaper This Day in Abuja and in Kaduna last week, killing at least four people in coordinated strikes.
"The President urges Nigerians to remain united in their condemnation and rejection of the terrorists who have shown even more clearly by their latest attacks on the media and the academic community that their objective is to destabilize the nation," a presidency statement said on Monday.
Africa's most populous nation, with more than 160 million people, is split roughly equally between a largely Christian south and a mostly Muslim north.
The unrest is piling pressure on southern Christian Jonathan to improve security in the north and honour pledges made during his election campaign to create jobs and reduce poverty, seen as the main cause of unrest in the region.
Diplomats say that will be near impossible in the most violent and impoverished northern areas, caught in a vicious circle of poverty and insecurity.
Additional reporting by Joe Brock, Camillus Eboh, Felix Onuah, Afolabi Sotunde and Mike Oboh in Abuja and Bello Buhari and Shuaibu Mohammed in Jos; Editing by Tim Cocks and Andrew Roche