Hundreds of protesters are rallying in Cairo's Tahrir Square demanding quick trials for ousted figures from the former regime of President Hosni Mubarak.
Egyptian media say organizers are calling the gathering "Friday of Retribution'' - a reference to their perceived slow pace of justice in Egypt under interim military rulers.
The demonstrations come after violent confrontations between police and protesters this week in central Cairo injured more than 1,000 people.
Witnesses say most of those injured in the protests that began late Tuesday and lasted into Wednesday suffered smoke inhalation from tear gas fired by police to disperse rioters who threw stones and burned tires.
The anger at the ruling military council continues even though Mubarak and his sons are to face trial in August for their alleged role in the deaths of protesters during the uprising that drove him from power in February.
The ex-leader and his two sons are also charged with crimes stemming back decades. Some top figures have already been tried and convicted on corruption and other charges.
Parliamentary elections are scheduled for September.
On Thursday, U.S. Secretary of State Hillary Clinton said the Obama administration will renew limited contact with Egypt's Muslim Brotherhood faction.
Egypt's Muslim Brotherhood recently joined with 17 political parties to establish what they call a pro-democracy platform for the elections. The coalition pledges to push for equality and democratic freedoms.
The Islamist Muslim Brotherhood is one of Egypt's most organized political movements and was banned under Mubarak's rule.
Some information for this report was provided by AP and AFP.