A bomb blast killed two Egyptian policemen and two civilians near the foreign ministry in central Cairo on Sunday, a security official said.
State television reported that a police officer and a conscript were killed in the blast in the crowded area on the Nile River which houses the foreign ministry and state television headquarters.
Live television footage showed the aftermath of the blast, which brought a tree down on a nearby car. Policemen with sniffer dogs were scouring the area for more bombs.
Militants have killed scores of policemen in bombings and shootings since Egypt's military toppled Islamist president Mohamed Morsi in July 2013.
Militants have in the past set off several bombs in succession, to target first responders after the initial attack.
Two policemen, both bomb disposal experts, were killed trying to defuse bombs outside the presidential palace in June.
