Seven people in northern Nigeria have been killed in two attacks blamed on Boko Haram, a radical Islamist group.

Witnesses say the dead include five police officers and two civilian bystanders.

Several Boko Haram members launched an attack on a police station in the town of Kankara in Katsina state late Monday. The other attack was on a bank in the same town. But there are conflicting reports about whether that attack was staged by Boko Haram members or by local bank robbers.

A police spokesman said Boko Haram is not interested in money.

The sect is trying to establish strict Sharia law across northern Nigeria. Boko Haram means “Western education is sinful” in the local Hausa language.

Boko Haram has claimed responsibility for last week's bombing of police headquarters in Abuja, the Nigerian capital, which left at least two people dead.

In recent years, the group has been blamed for a string of deadly attacks in Nigeria's north, targeting police officers and government officials.

Boko Haram is believed to have carried out many bombings and shootings in northern Nigeria, especially Borno state.

Boko Haram launched a brief uprising against the government in July 2009, sparking a heavy military response and a week of fighting that killed some 700 people.