The Islamist militant group known as Boko Haram has claimed responsibility for deadly attacks on Christian churches in northern Nigeria Sunday.

The claim came in the form of an e-mail sent to journalists from the group's purported spokesman, Abul Qaqa.

It said the group carried out the bombings because Christians have enjoyed government support while, in the words of the e-mail, “killing Muslims and destroying their mosques in northern towns.”

Two blasts hit churches in the city of Zaria Sunday, while a third took place at a church in the city of Kaduna.

Hundreds of people rioted after the bombing in Kaduna. Police stopped the unrest and the state governor imposed a 24-hour curfew.

Boko Haram has also claimed responsibility for church attacks the previous two Sundays. Those attacks killed 18 people.

The shadowy militant group has said it is fighting to establish a strict Islamic state throughout Nigeria. It does not recognize the government or the country's constitution.