Nigerian rebel group Boko Haram claimed responsibility for twin attacks on evangelical churches that killed at least four people and injured dozens more on Sunday.

“We launched these attacks to prove the Nigerian security wrong and to debunk their claim that we have been weakened by the military crackdown,” spokesperson Abul Qaqa said in the Hausa language during a conference call with reporters. “The Nigerian state and Christians are our enemies, and we will be launching attacks on the Nigerian state and its security apparatus, as well as churches, until we achieve our goal of establishing an Islamic state in place of the secular state.”

In the city of Jos on Sunday, a suicide bomber detonated his car bomb outside the church, while in the northeastern town of Biu, five gunmen stormed a service and opened fire. Both areas have been subjected to rebel violence in the past, and the attacks were the latest in Boko Haram's three-year-old insurgency.