* Boko Haram biggest security threat in Nigeria
* Sect blows up market in Maiduguri (Adds another attack, details, background, quotes)
KANO, Nigeria, Feb 6 (Reuters) - Gunmen attacked a police station with explosives and automatic weapons in Nigeria's northern city of Kano on Monday, the latest assault by suspected Islamist militants on the country's second biggest urban centre.
A Reuters reporter heard a powerful blast which shook windows and a sustained gun battle, which was still under way after more than an hour.
Boko Haram is waging a low level insurgency against the government and says it wants to impose sharia law across the country of 160 million people split evenly between Muslims and Christians.
Militants also blew up a pharmacy in a market area in the remote northeastern city of Maiduguri, Boko Haram's heartland, witnesses said. A Reuters photographer saw black smoke billowing from the building.
"The gunmen came from different directions to attack the Sharada industrial estate police station with bombs and gun shot some minutes after 6pm. One policeman was shot on the leg and he is receiving treatment in hospital," Kano police spokesman Magaji Musa Majia'a said by telephone.
"Our men at the station engaged them in a gun battle and as I speak to you now our men has taken over the place and are mopping up the area."
Boko Haram have become President Goodluck Jonathan's biggest security headache and a major distraction from plans to reform Africa's second biggest economy, as he has come under increasing fire for failing to quell the insurgency in the north.
The past three months have seen a surge in violence by the sect, a movement loosely modelled on Afghanistan's Taliban whose name means "Western education is sinful".
Kano was the scene of the deadliest attack by the Islamist sect Boko Haram, in which 186 people were killed last month.
Nigerian secret service sources said they arrested the purported spokesman for Islamist militant sect Boko Haram Abu Qaqa on Wednesday, although a man claiming to be him telephoned journalists from the sect's heartland of Maiduguri to deny it.
In an interview with Reuters on Jan. 26, Jonathan challenged Boko Haram militants to come out of the shadows and identify themselves as a basis for talks, an offer they have yet to take up. (Reporting by Mike Oboh and Bala Adamu in Kano; Writing by Tim Cocks; Editing by Tim Pearce and Andrew Heavens)
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