The blast targeted a police checkpoint in the Boulaq Abu el-Ela district.
The homemade bomb was planted beneath a tree outside the foreign ministry, said Tareq Abdel-Shafy, head of Boulaq Abu el-Ela district.
The militant attacks targeting police and military have increased after the ouster of Islamist President Mohamed Morsi last year.
Many policemen and soldiers have been killed in the attacks.
In July, militants attacked a military checkpoint in Al-Wadi Al-Gedid governorate in southern Egypt, killing 21 Egyptian border guards and injured four others.