Abuja, Nigeria (CNN) -- A militant Islamist group claimed responsibility Monday for bombings the day before that the Nigerian Red Cross said left 50 people at three Christian churches in Nigeria.

Boko Haram said the attacks Sunday in the Nigerian cities of Zaria and Kaduna were retaliation on Christians for destroying mosques and, according to the group, turning others into "beer parlour and prostitution joints."

Let them know that now it's the time for revenge God willing," the group said in a statement. "From now on, they either follow the right religion or there will be no peace for them."

Government and Red Cross figures on the death toll in Sunday's attacks differed. However, the bombings at two churches and a third in Kaduna left at least 50 people dead and 131 wounded according to the Red Cross.

he series of attacks began when a suicide bomber drove at high speed through a barricade at the EWCA Goodnews Wusasa Zaria church around 9 a.m., congregation member Lucy Bello said.