At least 10 people, including eight Coptic Christians, have been killed in a shooting outside a church and a nearby shop owned by a Christian in a Cairo suburb, Egypt's Health Ministry said.
It was the latest attack targeting the majority Muslim country's embattled Christian minority.
The attack outside the Coptic Church of Mar Mina left at least one policeman dead and five others wounded, including two critically, Health Ministry spokesman Khaled Megahed said.
The assailant was also killed, he added.
The shootout took place when a gunman on a motorbike tried to break through the security cordon set up outside the church, said the Interior Ministry.
An explosive device was in the assailant's possession when arrested, it added.
The attack comes amid tightened security around churches and Christian facilities ahead of the Coptic Orthodox Christian celebrations of Christmas on January 7.
Police have been stationed outside churches and in nearby streets across Cairo.
President Abdel-Fattah el-Sissi has chaired meetings with his top security chiefs to discuss security during New Year's Eve and the Orthodox Christmas.
A video circulating on social media after Friday's attack apparently shows the gunman lying on the ground with his face covered in blood. Authorities have closed off the area around the church.
The Interior Ministry said the assailant had earlier opened fire at a nearby shop.
The shootout outside the church and at the shop killed a total of eight people and a policeman, the ministry said.
The assailant was wounded in the gunfire exchange before his arrest, said the statement, which did not clarify whether he later died.
No group has yet claimed responsibility for the attack, which bore the hallmarks of Islamic militants who have for years battled security forces in Egypt's Sinai Peninsula in an insurgency now led by a local affiliate of the extremist Islamic State group.
The latest attack, in the southern Cairo suburb of Helwan, showcases the difficulties faced by security forces to contain an insurgency that is growing in sophistication and brutality.
Samir Gerges, a witness to Friday's church attack, said people inside the church closed the gates when the shooting began but that some bullets penetrated the building.
He said he was walking along a nearby street when the shooting broke out. He saw people running and some taking cover in a nearby restaurant.
Another witness, 40-year-old Raouth Atta, was praying inside the church when the violence broke out.
"Once the gunfire was heard, the gates were closed immediately," she said.
"People were terrified and wanted to check on their families in other buildings of the church. We stayed inside for 30 minutes before we were able to get out."
Ms Atta said that once she was able to leave she saw blood everywhere.
"We kept praying," said Father Boules, who was teaching a Sunday school class - which take place on Fridays and Saturdays - in the church complex.
On hearing gunfire, he went to check his students, who were panicking and terrified.
Since December 2016, Egypt's Copts have been targeted by the militants, who waged a series of attacks that left more than 100 dead and scores wounded.
The country has been under a state of emergency since April after suicide bombings struck two Coptic Christian churches on Palm Sunday.
The IS affiliate has claimed all the bombings targeting Christians.
Christians make up about 10% of Egypt's population. They have long complained of discrimination in the Muslim-majority nation, and claim authorities have often failed to protect them from sectarian attacks.