As rescuers tried to reach the wounded in the Malali neighbourhood of Kaduna, youths armed with machetes and clubs beat to death two Muslims passing by the smouldering ruins of St Rita's Catholic church.
A witness saw the men's corpses, as police and soldiers ordered those in the neighbourhood of Christians and Muslims to go home before more violence broke out.
Yesterday's car bombing was the latest high-casualty attack targeting churches. People now fear more reprisal killings, and religious violence could follow in Kaduna and elsewhere along Nigeria's religious faultline separating its largely Christian south from its predominantly Muslim north.
The attack happened around 9am as the reverend of the parish conducted Sunday worship. Witnesses said the suicide bomber ploughed his SUV past a gate and a security guard before ramming into the church's wall and detonating the explosives hidden inside the vehicle.
The blast left shattered glass and blood across the floors of the church's sanctuary. One of the brown walls of the church caved in and bore scorch marks from the blast.
Rescuers found the bodies of seven worshippers and the suicide bomber after the attack, said a spokesman for Nigeria's National Emergency Management Agency. He said more than 100 others were injured and taken to local hospitals.
Kaduna state police commissioner Olufemi Adenaike told journalists at the church that authorities had urged those living in the religiously mixed neighbourhood to return home and stay indoors to halt any further revenge attacks.
A spokesman for Kaduna state government said the rest of the city was peaceful.
A spokesman for President Goodluck Jonathan, said the nation's leader condemned the attack. He added: "The persistence of messengers of evil will not prevail over the will of the government and the people to secure peace and safety."
No group immediately claimed responsibility for the attack, which came as the Muslims were celebrating the end of Eid al-Adha holiday in Nigeria.
Rumours have circulated that the radical Islamist sect known as Boko Haram might try to launch an attack during the holiday. The sect has demanded the release of all captive members and called for strict Shariah law to be implemented across the country.
However, the group could not be reached for comment.
It has attacked churches with suicide car bombs in the past. A 2011 Christmas Day attack on a Catholic church in Madalla near Nigeria's capital, along with assaults elsewhere, killed at least 44 people. An unclaimed car bombing on Easter in Kaduna killed at least 38 people.
Christians and Muslims largely live in peace, work together and inter-marry in Nigeria, a nation of more than 160 million people.
However, Kaduna, a major city in Nigeria's north that has a large Christian population, has seen hundreds killed in recent years in religious and ethnic violence.
Shehu Sani, an activist who runs the Kaduna-based Civil Rights Congress, said: "Intolerance is eroding our liberties and insurgency is destroying our rights."