Egyptian security forces firing tear gas clashed with around 5,000 rock-throwing protesters in central Cairo late Tuesday, leaving dozens injured in the latest unrest to rattle the country, witnesses and medical officials said.

Clouds of tear gas and the wail of police sirens engulfed Tahrir Square as the security forces battled to regain control of the central plaza from the demonstrators, many of them family members of the more than 850 people killed during the revolution.

The families are frustrated with what they perceive as the slow prosecution of security officers believed to be responsible for the deaths of some 850 protesters during the 18-day uprising that ousted Hosni Mubarak in February.

As Tuesday's clashes moved into early Wednesday morning, rocks and shattered glass littered the streets around Tahrir, as protesters chanted: "Down with the military junta." The demonstrators used motorcycles to ferry the injured to safety.

The violence started outside the Interior Ministry after some protesters began throwing stones at the building, said Mohammed Ahmed, a 33-year-old eyewitness. Security forces responded with volleys of tear gas and blocked off the streets around the ministry.

The violence then shifted to nearby Tahrir Square, which was the epicenter of Egypt's revolution. Lines of central security troops in riot gear sealed off the main streets leading into the square, while dozens of security vehicles were parked in side streets.

Al Maataz Hassan, an engineer, accused the security forces of the same heavy-handed tactics as before Mubarak's fall.

"The security forces' violence is the same," he said. "They accuse the people of being thugs, then crackdown. It's the same mentality as before the revolution."

Tuesday's clashes, the most serious between security forces and protesters since the revolution, are a sign of the tumultuous transitional period the country is going through as it struggles to shift from an authoritarian to democratic system.

That transition took a step forward earlier Tuesday with an Egyptian court's ordering the dissolution of more than 1,750 municipal councils, seen as one of the last vestiges of Hosni Mubarak's rule.

The administrative court decision, announced by presiding judge Kamal el-Lamei, meets a major demand of the protest movement that drove Mubarak from the presidency in an 18-day uprising early this year.

The local councils, with over 50,000 seats filled by elections widely viewed as rigged, were a backbone of support for Mubarak's ruling party. They became particularly important after 2005 constitutional amendments required presidential candidates to obtain support from a quota of local council officials, as well as from national parliament members. Critics saw this as a stepping stone for Mubarak's son, Gamal, to succeed his father in office.

The court decision can still be appealed, but popular opposition may make it difficult for Egypt's current military rulers to challenge it.

Hamdi el-Fakharani, an engineer who filed the court case against the councils, said 97 percent of council members belonged to Mubarak's now-dissolved National Democratic Party.

"They had already begun campaigning, using municipal services to influence people in favor of the party's comeback and saying the revolution has negatively impacted the economy," he said.

He said he was joined in the complaint by 10 independent council members who attested to council corruption.

The dismissal of all council members will leave Egypt's municipalities under the control of unelected local executives and provincial officials, until new councils are elected.

A major rally is planned next week to, among other things, show support for dissolving the local bodies' membership. Activists say the councils, criticized as corrupt and flush with government funds, could help the campaigns of supporters of the former regime in parliamentary elections, scheduled for September.

"This is, of course, an important decision. If we are having parliamentary elections, these municipal councils were set to play a big role," said Hafez Abu Saada, a human rights lawyer who monitored and criticized the councils' 2008 elections.

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Associated Press writer Sarah El Deeb contributed to this report.