Four people including two policemen were killed and three soldiers wounded in a blast on Sunday near the Egyptian Foreign Ministry in Cairo, Xinhua reported.
Several explosive devices went off outside the entrance of a metro station and under a bridge opposite the ministry building.
According to official news agency MENA, the explosion occurred on a sidewalk in the lightly crowded neighborhood of Boulaq Abu Eila Street, under the May 15 Bridge where a security checkpoint is located.
Policemen with sniffer dogs were combing the area for more bombs. Six ambulances were rushed to the scene.
The attack came in the first day of the academic school year in Egypt. Students in five schools near the blast site were evacuated.
Also dozens of street vendors of the second hand clothes near the metro station were moved to safer places.
Since the ouster of the Islamist president Mohamed Morsi a year ago, surge of attacks and bombing targeting security men hit mostly Sinai Peninsula, the capital and some Delta cities in revenge for the security crackdown on his supporters.