A bomb exploded near a security checkpoint in northeast Cairo at dawn on Monday, injuring at least three, Al-Ahram Arabic news website reported.

The bomb was planted by unidentified assailants in Cairo's Hadaeq El-Qubah district. It blew up as a nightly patrol passed by, a security official told Al-Ahram.

Three security personnel were injured in the attack, with one in a critical condition, the source added.

Egypt has been rocked by political turmoil since the ouster of Islamist president Mohamed Morsi in July. A harsh crackdown on Islamists, in which thousands have been arrested, including Morsi, has raised fears some might take up arms against the state.

A high ranking police officer was assassinated in Cairo last week. An Al-Qaeda-inspired militant group claimed responsibility for the killing and said it was in retaliation for the arrest of Islamist women.

Recurrent attacks in the capital and other governorates have heighted fears that terrorist violence in the Sinai Peninsula could spill over into the rest of the country.

Since Morsi's ouster, Islamist militants have launched near-daily attacks against security and army targets in the peninsula, which adjoins Israel, killing dozens.

Ten Egyptian soldiers were killed by a car bomb in the peninsula on Wednesday, one of the deadliest attacks there since insurgents stepped up violence.