Cairo - An Egyptian police brigadier general was killed on Wednesday by a bomb placed under his car in Cairo, security officials said, in the fifth such attack targeting police in the capital within a week.

The explosion killed Ahmed Zaki, a commander in Egypt's central security forces, who have been at the forefront of a wide-ranging crackdown on supporters of ousted Islamist president Mohamed Morsi.

Militants have carried out scores of attacks mainly targeting security forces since the military deposed Morsi last July amid massive protests calling for his resignation.

Zaki was the third senior police officer to be killed in attacks since the start of the year.

In a separate incident, a police lieutenant was killed in a gunfight with wanted “terrorist elements” in the Mediterranean city of Alexandria on Wednesday, security officials said.

A little-known jihadist group, Ajnad Misr (Soldiers of Egypt), has claimed several attacks targeting police in the capital, and has vowed to launch more in retaliation for the crackdown on Islamist backers of Morsi.

But the deadliest attacks in Cairo and other parts of the country, including the restive Sinai Peninsula, have been claimed by Ansar Beit al-Maqdis (Partisans of Jerusalem), a jihadist group inspired by al-Qaeda.

Official figures show that about 500 people - mostly police and soldiers - have been killed in bombings and shooting attacks by militants in Egypt since Morsi's ousting.

Amnesty International says more than 1 400 people have been killed in the police crackdown on Morsi supporters.

More than 15 000 Islamists, mostly from Morsi's Muslim Brotherhood, have been jailed, while hundreds have been sentenced to death after often speedy trials.

Morsi was ousted by his army chief, Abdel Fattah al-Sisi, who is now the frontrunner in next month's presidential election.

The 59-year-old Sisi is riding a wave of popularity after ousting Morsi. Leftist leader Hamdeen Sabbahi is his only rival in the May 26-27 vote. - AFP