No one has claimed responsibility as of Friday morning, but the Islamic State has largely claimed responsibility for previous attacks on Christian churches in Egypt. One of the assailants fled the attack site and is being pursued by the security forces. Islamist militants have claimed several attacks on Egypt's large Christian minority in recent years, including two bombings on Palm Sunday in April and a blast at Cairo's largest Coptic cathedral in December 2016 that killed 28 people.
Two police officers were among those killed, reports said.
At least two people were reportedly killed in that attack.
The officials said a gunman opened fire outside a Coptic church before he was shot dead himself. It was the latest attack targeting Egypt's embattled Christian minority.
According to the Youm7 newspaper, the security forces are now trying to detain the second attacker, who left the scene riding a motorcycle.
A video circulating on social media after Friday's attack apparently showed the gunman lying on the ground with his face covered in blood.
IS claims responsibility:Islamic State (IS) claimed responsibility for the attack without providing evidence for the claim, while Interior Minister Magdy Abdel Ghaffar issued directives to security officials to raise the security alert to the maximum level across the country, in the wake of the foiled terrorist attack. Authorities closed off the area around the church.
Egypt's Interior Ministry referred to only one, but the Coptic Orthodox church mentioned "gunmen".
Egypt's state-run MENA news agency quoted an official anonymously as informing that the attack in Helwan was perpetrated by two attackers. A Muslim mob stabs 27-year old Coptic Christian Fam Khalaf to death in the southern City of Minya over a personal feud.
Smartphone users have begun posting footage of the attack online.