(Reuters) - Gunmen opened fire on a church service in Nigeria Thursday, killing six people and wounding 10, the church's pastor said, the latest in a string of attacks that has raised fears of sectarian conflict in Africa's most populous nation.

The attackers started shooting sporadically. They shot through the window of the church, and many people were killed including my wife, Pastor Johnson Jauro told Reuters by telephone from his Deeper Life church in Nasarawa, Gombe state in northern Nigeria.

Many of my members who attended the church service were also injured, he said.

The gun attack followed a warning from violent Islamist sect Boko Haram published in local newspapers on Tuesday that Christians had three days to leave majority Muslim northern Nigeria or they would be killed.

Analysts say it looks increasingly likely the group - or factions within it - wants to trigger reprisals from Christians against Muslims to bring on a full religious conflict.

The nation of 160 million is split roughly evenly between the two faiths.

The militant group also claimed responsibility for a series of bomb attacks across Nigeria on Christmas Day, including one at a church near the capital Abuja that killed at least 37 people and wounded 57.

Most Christians live in the south and most Muslims in the north, but many communities are mixed, and they usually live side by side in peace.

Gombe state's police commissioner was not immediately available to comment on the violence.

President Goodluck Jonathan declared a state of emergency in the northeast and two other regions in Nigeria on December 31, in a bid to contain a growing insurgency by Boko Haram, which says it wants to apply Islamic sharia law across Nigeria.

Heavily armed troops and tanks have been patrolling parts of northeast Nigeria since Jonathan made the announcement.

DIVISIONS STRAINED

The attacks targeting Christian houses of worship have strained Nigeria's increasingly fractious north-south divide.

Christian associations have accused Jonathan of not doing enough to contain the Islamist threat and said violence could provoke a sectarian civil war.

Two suspected Nigerian Islamist sect members were arrested on Thursday after an attack which killed two people, the military said, as authorities stepped up a crackdown on the increasingly violent group.

We have arrested two of the Boko Haram members who killed a man and his son in Dala on Wednesday night. They left behind their handsets through which we were able to trace them, said Colonel Victor Ebhemele, operations officer of the joint task force operating in Borno state.

Dala is a ward in Maiduguri, the capital of Borno, a remote dusty region which sits on borders with Cameroon, Niger and Chad which is at the heart of the Boko Haram insurgency. These borders were closed as part of Jonathan's emergency measures.

At least two bomb blasts shook Maiduguri on Wednesday, and a gun battle in another town killed at least one civilian, police said.

(Writing by Tim Cocks; Editing by Andrew Heavens)

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