Egypt said Monday it has dismantled three "terrorist cells" targeting security forces, including one run by jihadists and another operated by student supporters of ousted Islamist president Mohammed Morsi.

Militants have stepped up attacks on security forces since the army overthrew Morsi in July last year.

Egypt's next president will have to contend with frustrated workers who have threatened a new wave of nationwide strikes if their demands are not met by an already cash-strapped government.

Abdel Fattah al-Sisi, the ex-army chief who overthrew Islamist president Mohamed Morsi last July and is hailed by supporters as a tough leader who can restore stability, is widely expected to win next month's election.

A bomb blast in an upmarket central Cairo district wounded two policemen and a passer-by Tuesday, the latest attack on Egypt's security forces since Islamist president Mohamed Morsi was ousted.

The morning attack blew off the roof of a shelter manned by traffic police at a busy intersection in Al-Galaa Square in the Egyptian capital's Dokki neighborhood.

Two senior Egyptian army officers were killed during a raid on a jihadist hideout north of Cairo on Wednesday, as security forces close in on militants in the Nile Delta.

Six members of the Al-Qaida-inspired Ansar Beit al-Maqdis (Partisans of Jerusalem) group, which has been implicated in spate of attacks on security forces, were also killed in the hours-long shootout, the army and police said.

Gunmen killed six soldiers at a Cairo checkpoint Saturday in a brazen morning attack the military blamed on the Muslim Brotherhood movement of deposed President Mohammed Morsi.

The attack came two days after gunmen killed a soldier in Cairo, as militants once based in the Sinai Peninsula increasingly target the capital in a campaign that has killed more than 200 security men since the army overthrew Morsi last July.

A small bomb went off Tuesday evening on a bridge in the Egyptian capital without causing any casualties, a security official said.

The explosion in central Cairo caused only minor damage to the bridge's handrail, the official said.

The explosion of a suspected homemade bomb targeting a tram station in eastern Cairo wounded at least one person on Saturday, Egyptian security officials said.

Since the military ousted Islamist president Mohamed Morsi in July, militants have stepped up attacks against the security forces in Egypt, killing many soldiers and policemen.

Three people were killed and 28 wounded on Friday in Egypt as Islamist protesters clashed with security forces and civilian opponents, the health ministry said in a statement.

Meanwhile a security official told Agence France Presse 17 policemen were wounded in the capital Cairo, and that protesters torched three police cars.

Al-Mustaqbal movement leader former Prime Minister Saad Hariri held talks on Wednesday with Egyptian Deputy Prime Minister and Minister of Defense Field Marshal Abdel Fattah al-Sisi.

According to a statement issued by Hariri's press office, the two officials discussed the latest developments in the region.

Six Egyptian policemen were wounded in a bomb attack in Cairo on Friday, hours before clashes between police and Islamist protesters in several cities killed at least one person, officials said.

The attack shattered a tense calm in the capital after a spate of bombings on January 24 killed six policemen, in an escalation of a militant campaign following the overthrow of Islamist president Mohammed Morsi.