Egyptian security forces firing tear gas have clashed with several hundred rock-throwing protesters in the capital, Cairo, leaving dozens of people injured.

Clouds of smoke engulfed central Tahrir Square early Wednesday as police battled to regain control of Cairo's streets from demonstrators, many of them family members of the more than 850 people killed during the revolution that ousted President Hosni Mubarak.

The families are frustrated with what they see as the slow prosecution of security officers believed to be responsible for the deaths of protesters during the 18-day uprising.

The Interior Ministry blamed the clashes, which began late Tuesday, on a group of people who barged their way into a theater where a memorial service was being held to honor the “martyrs” killed during the uprising, prompting police to intervene.

Groups of protesters then moved to other areas, with some chanting, “Down with the military junta!”

The violence is the first in weeks to engulf Tahrir Square, the epicenter of the revolt that toppled Mr. Mubarak in February. It is also a sign of the tumultuous period the country is going through.

The transition took a step forward early Tuesday when an Egyptian court ordered the dissolution of the country's municipal councils, which were elected under Mr. Mubarak and dominated by his supporters.

The Cairo administrative court issued the ruling in response to complaints by citizens who accuse the councils of being corrupt.

Mr. Mubarak's now-dissolved National Democratic Party won more than 90 percent of the seats in the last local council elections in 2008, a vote that government critics said was rigged.

Disbanding the councils was one of the demands of the mass protest movement that forced Mr. Mubarak to resign in February after three decades of autocratic rule.

Tuesday's court ruling can still be appealed by the Egyptian military chiefs who took over from the ousted president. The dismissal of council members will leave Egypt's municipalities under the control of unelected bureaucrats until new councils are elected.

No date for municipal elections has been set.

Egypt is due to hold parliamentary elections in September followed by a presidential vote as part of the military's pledge to hand power to a civilian government.