Kenyan police say a grenade attack at a church in the capital, Nairobi, Sunday killed a nine-year-old boy and wounded three other children.

Police chief Moses Ombati says he believes sympathizers of al-Shabab Islamic militants were responsible.

Police say the children were at a Sunday school service at Saint Polycarp Church in Nairobi when someone threw a grenade into the building.

Authorities also believe al-Shabab supporters shot and killed two officers on patrol in the city of Garissa, near the border with Somalia Sunday. The attackers stole the officers' rifles.

Al-Shabab militants are struggling to hold on to the few remaining areas they control in Somalia, where Somali and African Union forces stymied their efforts to set up a conservative Islamic state.

Al-Shabab has threatened revenge attacks in Kenya, whose soldiers took part in the operations in neighboring Somalia.

Kenyan forces pushed into Port Kismayo Friday, forcing the militants to retreat from their largest remaining stronghold in Somalia.

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