Human Rights Watch on Tuesday called on the Nigerian government to take further steps to end what it called the “campaign of terror” by the militant Islamist sect Boko Haram.

The U.S.-based human rights group said Boko Haram is responsible for the deaths of at least 935 people since the beginning of its violent campaign in 2009, including 250 people in the first weeks of 2012. It said the majority of the attacks have been carried out in the northeastern Borno state, where the group is headquartered.

Most recently, the sect claimed responsibility for Friday's series of car bombings and other attacks that killed at least 185 people in Nigeria's second largest city, Kano.

Nigerian President Goodluck Jonathan has declared a state of emergency in much of the northern part of the country as part of efforts to stop the violence.

But Human Rights Watch on Tuesday said the government should do more to ensure those responsible are brought to justice. It also called for increased police presence in violence-stricken areas.

It said Boko Haram was targeting people in northern Nigeria based on religion and ethnicity, saying the increasingly sophisticated and deadly attacks show a “complete and utter disregard for human life.”

Meanwhile, tensions are high and security has been tightened in Kano after police discovered 10 car bombs and hundreds of other unexploded devices on Monday.

Boko Haram is reportedly fighting to implement its interpretation of Sharia law across Nigeria, a country of 150 million people that is divided between the mostly Muslim north and the largely Christian south.

The ongoing violence has raised concerns that Nigeria, Africa's most populous nation and biggest oil producer, is sliding toward civil war.