The radical Islamist group Boko Haram claimed responsibility for two church attacks that killed at least six Christians in Nigeria this weekend.
    
In Jos, a suicide bomber detonated a car bomb outside the Christ Chosen Church of God Sunday, collapsing part of the building.

At least four people died and 40 were wounded.
 
Angry Christians later gathered at the site, striking back at local Muslims.

Meanwhie in the northern Nigerian city of Biu, a gunman opened fire on a congregation during service, killing an usher and a church member.

Boko Haram has stepped up its attacks on Christians over the last several months. The radical Islamists most recent attack took place Tuesday. A retired deputy inspector-general of police and two other officers in Kano were killed in drive-by assault.