The news website Sada El-Balad cited a source in the investigation team as saying an unknown attacker threw a bomb inside the cathedral during a prayer service.
A dozen of ambulances have arrived at the scene of the explosion, the local news website Youm7 said. No armed group has reportedly claimed responsibility for it.
There has been no claim of responsibility yet.
The cathedral in the Egyptian capital’s Abbassia district serves as the seat of the Coptic Orthodox Pope. Copts are a large ethnic and religious minority in Egypt.
SPUTNIK/MNA