At least four people have died in bomb and gun attacks on two churches in Nigeria.

The violence in Jos and Biu, a city in north-eastern Borno state, comes as almost every weekend this year has seen churches targeted by a radical Islamist sect known as Boko Haram.

While no group immediately claimed responsibility for today's dual attacks, they bore the hallmarks of the sect's previous assaults, which continue despite a heavy military presence.

In Jos, a city on the uneasy dividing line between Nigeria's largely Muslim north and Christian south, a suicide car bomber drove toward the compound of the Evangelical Church Winning All chapel in the city and detonated his bomb nearby, said police.

The shock wave brought down a portion of the building, causing injuries inside.

Angry youths later surrounded the area, striking back against Muslims in retaliatory violence, witnesses said. Two people and the suicide bomber were killed, while more than 40 others were wounded.

Meanwhile in Biu, a city in north-east Nigeria's Borno state, gunmen opened fire during a service at an EYN church, an acronym that means "Church of the Brethen in Nigeria" in the local Hausa language of Nigeria's north, witnesses said. An usher and another worshipper at the church were killed in the attack while others were injured.

Nigeria faces a growing wave of sectarian violence carried out by Boko Haram, whose name means "Western education is sacrilege" in Hausa. Boko Haram has been blamed for killing more than 560 people this year alone.

The sect's targets have included churches, police stations and other security buildings, often attacked by suicide car bombers across northern Nigeria.