• 'Many killed and wounded' in north-east and central Nigeria
• Attacks bear hallmark of Islamist terror group Boko Haram
Two churches in northern and central Nigeria have been attacked, one by gunmen and the other by a suicide bomber, witnesses said.
There was no immediate word on casualties and no claim of responsibility. Attacking churches has become a trademark tactic of the Islamist group Boko Haram.
In Biu Town, in north-eastern Borno state, witnesses said three gunmen started firing at people outside a church before entering the main building. "Many people have been killed and wounded," said Hamidu Wakawa, who was at the church.
In the south-western city of Jos, a man drove a car to the entrance of the Christ Chosen church and detonated a bomb, said Emmanuel Davou, 53, who lives nearby.
Christian youths set up roadblocks and had to be dispersed by police, he said. "Angry youths have gone wild, even attempting to prevent the security personnel from getting to the scene of the incident. They had to force their way out by shooting in the air to disperse them."
The police spokesman for Borno state, Samuel Tizhe, said five gunmen attacked the church, killing one woman and wounding three other people, before they fled.
Police casualty figures from Islamist attacks are often lower than those given by witnesses caught up in them.
In the attack in Jos, a man drove a car to the entrance of the Christ Chosen Church and then blew it up, said Emmanuel Davou, 53, who lives nearby.
Emmanuel Ayeni, police commissioner for Plateau state, of which Jos is the capital, told journalists 41 people were being treated for injuries in a local hospital.
"The circumstances of the two killed by mobs is still unclear," he said.
Boko Haram has been blamed for hundreds of killings over the past two years. Its leader, Abubakar Shekau, frequently says attacks on Christians are revenge for killings of Muslims in Nigeria's volatile "Middle Belt", where the largely Christian south and mostly Muslim north meet and sectarian tensions run high.
The group usually targets security forces, although attacks on Christian worshippers are increasingly common. Last Sunday a suicide car bomber killed at least 12 people at a church in the remote northern town of Yelwa.