Unknown assailants have killed at least 11 people protesting against Egypt’s ruling generals near the defence ministry in Cairo, officials say.

The attackers set on them at dawn using rocks, clubs, firebombs and firing shotguns. The protesters retaliated, beating some of the assailants.

Soldiers and police have now stopped the clashes, but the intervention came nearly six hours after they began.

Two leading presidential candidates have suspended campaigning in protest.

Abdul Moneim Aboul Fotouh, an independent Islamist, and Mohammed Mursi, head of the Muslim Brotherhood’s Freedom and Justice Party (FJP), criticised the authorities’ response.

In addition, the FJP and the Salafist Nour party, which together control 70% of the seats in parliament, decided to boycott a meeting with the ruling Supreme Council of Armed Forces (Scaf).