Gunmen in northeastern Nigeria killed at least six people early Tuesday when they opened fire at a church during a Christmas Eve service.

Officials and residents say the attack happened shortly after midnight in a village outside the city of Potiskum in Yobe state. There was no immediate claim of responsibility.

Yobe is next to Borno state, the home of Islamic radical sect Boko Haram. Rights groups say the militants have killed well over 1,000 people in the past four years.

Boko Haram attacked churches at Christmas in both 2010 and 2011. Last year's attacks killed more than 40 people.

The group is fighting to impose a strict form of Islamic law in northern Nigeria, where Muslims are the majority.

In his traditional Christmas message on Tuesday, Pope Benedict prayed for peace in Nigeria, where he said savage acts of terrorism continue to reap victims, particularly among Christians.