Three men arrived at a central Nigerian church just before Bible study began Monday night and opened fire, killing at least 19 people in an attack that shows violence already seen elsewhere in the divided nation is spreading.

Worshippers arrive at Holy Trinity Catholic Church in Nigeria's capital Abuja on June 24. Some churches in northern Nigeria, usually packed with worshippers, have been almost empty on Sunday mornings after violence in religiously mixed Kaduna state. The latest attack hit a church in Okene, 250 kilometres to the south. (Afolabi Sotunde/Reuters)

Witnesses and the military described a chaotic, blood-soaked scene at the Deeper Life Church in Otite, a quiet neighbourhood on the outskirts of the city of Okene, 250 kilometres southwest of Nigeria's capital Abuja.

Two gunmen sprayed the windowless sanctuary Monday night with fire from Kalashnikov assault rifles, said Lt.-Col. Gabriel Olorunyomi, the head of a local joint army and police unit. Another armed man stayed back and switched off the generator providing lights in the church, leaving those inside unable to flee as the gunfire flashed through the darkness, witness Lawan Saliu said. Saliu spoke from a hospital bed Tuesday after sustaining a gunshot wound to his stomach.

It remained unclear how many people were wounded in the attack. Olorunyomi said some of the injured sought care in hospitals, while others remained at home. A rescue official, who spoke on condition of anonymity as officials had yet to publicly release casualty numbers, said there likely were fewer than 20 people wounded in the attack.

Soldiers and police officers searched for gunmen through the night, but had made no arrests as of Tuesday afternoon, Kogi state police spokesman Simon Ile said. No group immediately claimed responsibility for the attack.

Later on Tuesday, three gunmen on a motorcycle shot at a military patrol vehicle in Okene, said Olorunyomi. Police said two soldiers were killed in the attack.

The attack comes as Nigeria faces continuing attacks from a radical Islamist sect known as Boko Haram. Boko Haram, whose name means "Western education is sacrilege" in the Hausa language of Nigeria's Muslim north, has attacked churches in the past. They have also attacked mosques.

Although they have not previously claimed responsibility for attacks on places of worship this far south, authorities have said they raided a bomb factory run by suspected sect members in Okene in April. They also blamed Boko Haram for a February prison break in the town of Koton-Karifi , also in Kogi state that freed 119 inmates. That attack mirrored a massive prison break in the northeastern city of Bauchi in September 2010 when Boko Haram freed about 700 inmates.

The sect is blamed for more than 660 killings this year alone in Nigeria, according to an Associated Press count.

Nigeria, a nation of more than 160 million people, is largely divided into a Muslim north and Christian south. While members of the two faiths often live and work together, as well as intermarry, Boko Haram attacks have increased religious tensions in the nation over the last year.