CAIRO, Egypt — Egyptian security forces have fired tear gas on protesters in central Cairo after violent clashes that left several injured, an AFP photographer said.

Tahrir Square, the epicentre of protests that toppled president Hosni Mubarak, was sealed off and authorities cut off electricity in the area.

Police continued to fire tear gas into the early hours of the morning and a thick white cloud hung over the square.

A reporter for Egyptian satellite channel al-Hayat described the scene as "a street war between riot police and protesters."

The trouble started when a group of people stormed a theatre where a memorial service was being held for those killed in the uprising that toppled president Hosni Mubarak in February, the official said.

He said the group then headed to the state TV and were joined by hundreds who began to throw rocks before heading to Tahrir Square.

But activists said the families of the victims had been denied entry to the memorial in Cairo and were beaten by police.

"After being denied entry .... clashes erupted between protesters and security guards at the theatre. The police showed up and started beating the families of martyrs," pro-democracy activist Arabawy wrote on his blog.

Witnesses told AFP that buses unloaded young men armed with sticks and knives, accusing remnants of the old regime of stirring chaos.

When protests erupted on January 25 to demand Mubarak's ouster, the veteran leader's loyalists used hired thugs to beat back protesters.

Tuesday's clashes erupted just hours after a Cairo court ordered the dissolution of local councils, which were dominated by Mubarak's National Democratic Party.

"I don't think the timing of these clashes is a coincidence," said one witness to satellite channel ON TV.

"It came just after the dissolution of the local councils, a decision which I'm sure will make many people (from the old regime) very angry," the witness in Tahrir Square said.

Television footage showed protesters chanting: "the people demand the fall of the Field Marshal," referring to Hussein Tantawi, the head of the Supreme Council of the Armed Forces, which took power when Mubarak stepped down.

Protesters who first took to the streets to demand the overthrow of Mubarak, began shifting their anger towards the ruling military council, accusing it of using Mubarak-era tactics to stifle dissent.

Activists have called for a massive rally on July 8 aimed at keeping up the pressure for democratic reforms.