The explosion targeted a police car under the Al-Qobba Bridge near to the presidential palace in Hadayeq Al-Qobba.
"A small bomb exploded near the Al-Qobba presidential palace in Cairo today morning, injuring a woman," police was quoted as saying by the Al-Ahram news website.
A police officer discovered the bomb but it exploded before the arrival of explosives experts, police said.
The new blast came a day after an explosion yesterday in the last bogey of a train that killed four people including two policemen and injuring ten others in Menouf, a city in the Nile Delta, the Egyptian TV reported.
Islamist militant attacks targeting police and military increased after the ouster of president Mohammed Morsi last year.
Over 500 policemen and soldiers army officers were reported killed in the attacks.
