Gunmen blew up a police station and shot one officer in Nigeria's flashpoint city of Kano on Monday as blasts rocked a market in Maiduguri, the base of the Boko Haram Islamists, police said.

Boko Haram has claimed a series of recent attacks in Africa's most populous nation and top oil producer, including coordinated gun and bomb assaults on January 20 in Kano, Nigeria's second city, that killed at least 185.

Gunmen have attacked two more police stations in Nigeria's second city of Kano, killing at least two people amid a wave of escalating violence blamed on Islamists.

One of the attacks occurred at dawn on Monday, setting off a gunbattle with police, residents said. On Sunday night, gunmen stormed another police station near a bus station, leaving two civilians dead.

Gunmen have killed 15 village traders returning from a market at night and set their bodies ablaze in northern Nigeria's Zamfara state, a local police chief said on Friday.

"Gunmen, suspected to be armed robbers, attacked some local traders on their way back from a market in neighboring Katsina state late Thursday," Zamfara state police commissioner Tambrai Yabo told Agence France Presse.

Gunmen on Thursday abducted a German engineer working with a construction company on the outskirts of the violence-hit Nigerian city of Kano, police said.

A driver along with two other assailants "came and abducted the engineer Raupach Edgar, attached to Dantata and Sawoe construction company," said police spokesman Magaji Majia.

Nigeria has made some 200 arrests after last week's bombings and shootings in the city of Kano, with most of those detained Chadian "mercenaries", a senior police source said Thursday.

"Many arrests have been made since the attacks," the police source said on condition of anonymity because he was not authorized to speak publicly following Friday's attacks that killed at least 185 people.

Fresh explosions and gunfire early Tuesday rocked an area near a police station in the Nigerian city of Kano, where coordinated attacks claimed by Islamists and shootouts left at least 185 dead last week.

Some 15 blasts and gunshots were heard coming from the vicinity of a mobile police headquarters. Details were not immediately clear, and police were not available for comment.

Nigerian police found eight bomb-laden cars in the northern city of Kano Monday as clerics said peace prayers after attacks that left over 160 people dead and stoked fresh fears of civil unrest.

President Goodluck Jonathan, facing his worst crisis of his nine-month tenure as he grapples with a surge in attacks by the Islamist sect Boko Haram and mounting social discontent, vowed to beef up security.

President Goodluck Jonathan visited Nigeria's second largest city of Kano on Sunday after at least 166 people were killed in one of the deadliest waves of attacks in the mainly Muslim north.

Jonathan, facing the biggest crisis of his rule, arrived in the city two days after the coordinated bombings and gunbattles rocked Kano in attacks claimed by the Islamist militant group Boko Haram.

Foreign Minister Adnan Mansour assured on Saturday that the Lebanese community in Nigeria is safe, noting that they were not harmed by the security incidents in that country.

According to the National News Agency, Mansour telephoned Lebanese ambassador to Nigeria Iman Younis inquiring about the situation.

Bomb attacks targeting security forces and gun battles killed at least 162 people in Nigeria's second-largest city of Kano, sources said, as bodies littered the streets on Saturday.

A curfew was imposed on Kano in Nigeria's mainly Muslim north after it exploded into violence on Friday evening, with eight police and immigration offices or residences targeted.