Lagos , Nigeria ( CNN ) -- Militants launched a fresh attack Monday in Nigeria 's second largest city , Kano , which is already reeling from a series of bombings and shootings that killed more than 200 people earlier this month . A police station in Mandawari was attacked at 6 a.m. , just after the dusk-to-dawn curfew was lifted , police said . No one was hurt . Hours earlier , gunmen on motorbikes hit a police station in Naibowa , killing two people . The Sunday evening attack lasted about 40 minutes , said Sani Abdu , a resident who lives close to the station . No one immediately claimed responsibility , but suspicion fell on the militant group Boko Haram , which has carried out multiple bombings and shootings across the north in recent days . On January 20 , at least 211 people were killed in Kano in attacks that left the police headquarters and other government buildings in charred ruins . In response , President Goodluck Jonathan fired the west African nation 's inspector general of police . Depending on the faction , Boko Haram 's ambitions range from the stricter enforcement of Islamic Sharia law to the total destruction of the government . Its grievances remain local , but it has attacked international institutions -- - such as the United Nations -- on Nigerian soil . An August 26 attack -- during which a Boko Haram suicide bomber drove a Jeep laden with explosives into the U.N. headquarters in Abuja -- was one of the deadliest in the world body 's history . Twenty-four people were killed , including 12 U.N. staff . The group was formed in 2002 by Islamic preacher Mohammad Yusuf as an outgrowth of ethnic tensions in the country in the 1990s . Nigeria 's population is split between mostly Muslims living in the north and predominantly Christians in the south . Yusuf advocated the institution of Sharia law throughout the northern states and opposed democracy . The group operated openly out of northeastern Nigeria and staged small-scale attacks against government targets . In 2009 , Nigerian police forces moved to crack down on Boko Haram . Harsh police tactics led to an armed uprising and the arrest of Yusuf , who later died in police custody . The death spurred the group to begin its attacks on police stations . Ensuing clashes between group members and the police killed hundreds . Journalist Hassan John in Jos contributed to this report .
Attacks on police stations are becoming commonplace . Recommend0 The group has been blamed for a wave of violence .