Six children and one teacher were injured after a homemade bomb was thrown at an Islamic school in Nigeria on December 27, MSNBC is reporting. The children were all under the age of nine, and at least one was as young as four-years-old. The attack occurred in a predominately Christian area in the city of Sapele. When the attack occurred, approximately 50 children were gathered for an Arabic class.

Charles Muka, the Delta State police spokesman, confirmed attackers drove by the school and threw the explosives into the classroom. Investigators believe a local vigilante group was behind the attack.

The incident comes after coordinated attacks by radical Islamist militants on Christmas Day. Those attacks killed at least 39 people. The recent attacks risk reviving sectarian violence between the mostly Muslim north and Christian south. The conflict between the two sides has claimed thousands of lives in the past decade.

Boko Haram, the radical Muslim sect, has claimed responsibility for the church attacks, as it aims to impose Islamic Shariah law across Nigeria. The Christmas Day bombings have led many northern Nigerian Christians to fear a religious war with the country’s southern Muslims. However, there’s currently no belief that the church bombings are linked to the school attack.

Written by: Karen Benardello