Dozens of people are feared dead and injured after two separate attacks on churches in Nigeria during Sunday service, the government said.
A suicide bomber blew himself up near a church in the central city of Jos on Sunday, while gunmen attacked another church in Biu in the country's northeast.
Armed Islamist sect Boko Haram later claimed responsibility for both attacks, a purported spokesman for the group said.
Nigerian government spokesman Pam Ayuba said a bomb exploded near an evangelical church in Jos, a restive city on the dividing line between the nation's Muslim north and Christian south, causing casualties.
"The suicide bomber attempted to drive into the Christ Chosen Church in the Jos metropolis," Al Jazeera's Yvonne Ndege reported from Lagos on Sunday.
"The chief of police has spoken to the local press there [in Jos], and he says that three persons have been killed in this attack. One of them, the suicide bomber, and two others died in unclear circumstances."
Our correspondent said the two others died after chaos and violence broke out following the blast, with people angry that the authorities were not doing enough to protect them.
"Police have announced that 48 people have been taken to various hospitals in the Jos metropolis with varying degrees of injuries," Ndege said.
Earlier, in Biu, a city in northeast 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.
"Before the Jos attack, we know that gunmen burst into a church in the town of Biu just outside of Maiduguri, the capital of Borno state. These gunmen opened fire on members of a church who were worshipping," our correspondent said.
Gunmen sprayed the congregation with bullets, killing and wounding many of them, witnesses said.
"Three gunmen came to the premises of the church and started firing at people outside the church before going into the main building to carry on their killings ... Many people have been killed and wounded," said witness Hamidu Wakawa, who was at the church in Biu Town.
Borno state police commissioner Bala Hassan confirmed the attack took place and said officers were investigating.
"The picture is very sketchy from there because it is so remote. It's not clear at this stage how many people may have been killed in this attack. Eyewitnesses on the ground say people have died, but the police on the ground have not come out with a statement yet," Ndege said.
Speaking to journalists on a conference call on Sunday night, a purported spokesman for Boko Haram - an armed group that seeks to impose Islamic law in Nigeria - claimed both attacks.
"We are responsible for the suicide attack on a church in Jos and also another attack on another church in Biu," the spokesman calling himself Abul Qaqa said.
"We launched these attacks to prove the Nigerian security wrong and to debunk their claim that we have been weakened by the military crackdown."
Attacking churches has become a trademark tactic of Boko Haram, which has linked up with other Islamist groups in the region including al-Qaeda's North African wing.
The group has become the biggest security threat in Nigeria. It usually targets security forces, although Christian worshippers are increasingly bearing the brunt of attacks.