Police fired tear gas at dozens of stone-throwing protesters in Cairo on Sunday, Jan 27 in a fourth day of street violence that has killed at least 41 people and compounded the political challenges facing President Mohamed Mursi, Reuters reported.

The most deadly clashes flared up in Port Said where 32 people were killed on Saturday alone. That violence was provoked by a court verdict sentencing 21 people, mostly from the city, to death for their role in a deadly stadium disaster last year.

But protests have been going in cities across Egypt since Thursday led by opponents of Mursi and his Islamist allies. Demonstrations were initially timed to mark Friday's second anniversary of the uprising that overthrew Hosni Mubarak.

Opponents say Mursi has betrayed the goals of the revolt.

The army, Egypt's interim rulers until Mursi's election June, were sent back onto the streets to restore order in Port Said and Suez, another port city on the Suez Canal where at least eight people have been killed in clashes with police.

Although scuffles continued on Sunday morning in Cairo, there was no immediate sign of the kind of deadly escalation of previous days in the capital or elsewhere.