KANO, NIGERIA —
Gunmen stormed a police station and a bank in a town in Nigeria's northwest, beyond a region covered by a military crackdown on a Islamist insurgency, a sign the offensive could provoke violence by smaller militant cells across the north.
It was not clear who carried out the attack.
Several gunmen were killed during a clash with police in the remote town in Katsina state, army spokesman Ikedichi Iweha told Reuters, without giving specific figures or police casualties.
Major attacks blamed on Nigeria's Boko Haram
July - Attacks prompt government crackdown in Bauchi and Maiduguri; 800 people killed
December - Bombings in central Nigeria and church attacks in the northeast kill 86
June - Attack on a bar in Maiduguri kills 25
August - Suicide bomber kills 23 at U.N. building in Abuja
November - Bombings in Damaturu and Potiskum kill 65
December - Christmas Day bombings across Nigeria kill 39
January -- Gun and bomb attacks in Kano up to 200
February - Maiduguri market attack kills 30
June - Suicide car bombings at three churches kill 21
July - Attacks in Plateau state kill dozens, including two politicians at a funeral for the victims
February - French family kidnapped in Cameroon, held hostage for two months
April - Fighting with troops in Baga kills up to 200; residents say troops set deadly fires
May - Attacks in Bama kill more than 50
July - Gunmen kill 30 at a school in Yobe
August - Gunmen kill 44 at a mosque outside Maiduguri
September - Gunmen kill 40 students at a post-secondary school in Yobe
December - Militants attack military installations in Maiduguri
January - Militants kill 74 people and burn down a village in attacks in Borno and Adamawa
February - Gunmen kill as many as 60 in attack on school in Yobe
April - Militants abduct 276 schoolgirls
Nigerian forces are trying to regain territory controlled by increasingly well-armed Boko Haram Islamist insurgents in their northeastern stronghold states of Borno, Yobe and Adamawa, which were put under a state of emergency by President Goodluck Jonathan on Wednesday.
Security experts believe a crackdown in the northeast could push insurgent attacks into other regions, or awaken smaller cells that operate in other parts of the north.
"It's difficult to tell if this is a criminal attack or part of another Islamist cell,'' one security source said. "There have been incidents in the past in Katsina but it
certainly hasn't been an insurgent stronghold.''
Another security source said a bank was raided and prisoners were freed from the police station.
Boko Haram, other Islamist groups like al-Qaida linked Ansaru and associated criminal gangs have become the biggest threat to stability in Africa's second largest economy and top oil producer.
Thousands have been killed since Boko Haram launched an uprising almost four years ago in an effort to create an Islamic state in a country of around 170 million split roughly equally between Christians and Muslims.
Violence has mostly happened far from economic centers such as the commercial hub Lagos or political capital Abuja and hundreds of miles away from oilfields in the southeast.
Military jets, helicopter gunships and thousands of troops are involved in the current offensive, which may answer some critics who accuse Jonathan, a southern Christian, of underestimating the severity of the crisis in the Muslim north.
Rights groups are concerned the state of emergency will lead to more abuses by Nigerian forces.