An Egyptian police officer was killed and two wounded while trying to defuse a bomb planted near a Cairo church on Saturday.
The explosion was the latest in a series of incidents apparently targeting Egypt's Coptic Christian population, occurring the day before Orthodox Christmas eve and just a week after President Abdel Fattah El Sisi ordered the formation of a new agency to address sectarian incidents.
Some time on Saturday four explosive devices were planted around the Church of the Virgin Mary and St Mercurius in the Ezbet Al Haggana district of Nasr City, a priest at the church told local media.
Three were removed safely but the fourth, concealed in a bag, exploded when police bomb disposal technicians attempted to deactivate it. Police Major Mostafa Ebeid was killed in the blast, which wounded two other officers and a bystander.
Earlier, police had been notified after an imam at the neighbouring mosque warned church security about suspicious activity, father Barsoum Saadallah told local website Mada Masr.
There was no immediate claim of responsibility but previous attacks have been carried out by extremists .
Egyptian security forces have increased their presence outside churches before Coptic Christmas, which is celebrated on January 7.
Church leaders said they were concerned for their congregants. "Praying safety for those celebrating the #NativityFeast in our churches across Egypt, and those keeping them safe," Archbishop Angaelos of the London Coptic Orthodox Church wrote on Twitter.
President El Sisi was scheduled to inaugurate a new cathedral in the country's new administrative capital outside Cairo on Sunday. He is expected to attend Christmas eve Mass alongside Pope Tawadros II at the Cathedral of the Nativity, which with space for 8,200 worshippers, Egypt claims will be the largest in the Middle East.
Copts make up about 10 per cent of Egypt's 90 million population, but complain of discrimination and insufficient protection by they state. They have long complained about the difficulty of opening new churches, the construction of which are often blocked for security reasons.
Since December 2016 extremists have killed over 100 Egyptian Christians in attacks on religious sites.
In November, militants killed seven people returning from the baptism of a child at a Coptic monastery about 260 kilometres south of Cairo.
Last year, attacks in Alexandria and Tanta targeted Coptic churches on Palm Sunday, killing 47 and injuring more than 120.