Blast targets a vehicle carrying security forces in the capital's Maadi area, injuring four others.
A roadside bomb explosion near the Cairo suburb of Maadi has killed an Egyptian policeman and injured four others, according to the interior ministry.
"At about 12:45am on June 18 as a vehicle belonging to the Central Security Forces transported a group of officers and conscripts an improvised explosive device planted on the roadside went off," the ministry said in a statement on Sunday.
"This led to the martyrdom of First Lieutenant Ali Abdelkhaliq and the injury of four others, an officer and three conscripts, who have been taken to hospital for treatment."
The bomb was detonated remotely, and an initial examination suggested it was detonated using a mobile phone SIM card, a senior interior ministry official told state news agency MENA.
A joint task force made up of several police units is questioning tenants of flats overlooking the site of the attack to try to identify and arrest the culprits, the official said.
Egypt faces an unrest led by the Islamic State State of Iraq and the Levant (ISIL) group in the Sinai Peninsula, where hundreds of soldiers and police have been killed since 2013.
ISIL, also known as ISIS, has also increasingly carried out attacks in the mainland on security forces and Coptic Christian civilians in recent months, killing about 100 Copts since December.
Other armed groups are active in Cairo and other cities where they have targeted security forces, judges, and pro-government figures.