Clashes between Egyptian security forces and protesters in Cairo have injured more than 40 people Wednesday as demonstrators called for the country's field marshal to step down.

Demonstrators are frustrated with what they see as the slow prosecution of security officers believed to be responsible for the deaths of protesters during an 18-day uprising earlier this year. They accuse Field Marshal Mohammed Hussein Tantawi of deliberately slowing down cases against top officials from the regime of ousted President Hosni Mubarak.

Egyptian security forces fired tear gas Wednesday as several protesters hurled rocks in the capital's Tahrir Square, the epicenter of the revolt that toppled Mr. Mubarak in February.

Clouds of smoke engulfed the square 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.

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. It is also a sign of the tumultuous period the country is going through.

Egypt's transition took a step forward early Tuesday when a court ordered the dissolution of the country's municipal councils that 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.

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.