Activists threw Molotov cocktails at police, who responded by firing birdshot, Egypt Independent reported. The clash came during the afternoon, after a brief break in the confrontation between police and protesters.
Egyptian President Mohamed Morsi Thursday granted himself new powers and named a new prosecutor general, who said former President Hosni Mubarak would be retried.
Morsi issued a decree stating that all decisions he has made since taking office are not subject to review or appeal, The Washington Post reported.
Shortly after Morsi named Talaat Ibrahim Abdallah to succeed Abdel Meguid Mahmoud as prosecutor general, Abdallah announced he would retry Mubarak, former Interior Minister Habib al-Adly and other former Mubarak-era officials on charges of killing protesters, al-Masry al-Youm reported.
Mubarak and Adly were sentenced in June to life in prison for their roles in the killing of protesters in Tahrir Square last year, but Adly's aides were acquitted. Egypt's Truth Seeking Committee said in October Mubarak, Adly and his aides should be retried.
"If a danger arises that threatens the January 25 revolution," the decree issued by Morsi read, the president "can take any procedures and preparations that he sees necessary to face this danger," the Post reported.
Some Egyptian TV commentators immediately suggested the decree suggested Morsi was creating a "dictatorship," and protesters began to gather in Tahrir Square -- some holding posters with images of Morsi and Mubarak.
Morsi supporters assembled at another location in Cairo to demonstrate in favor of the proclamation, the Post said
Fighting in the Tahrir Square area began Monday, as protesters observed the first anniversary of a demonstration last year on Mohamed Mahmoud Street.
Officials announced Wednesday at least 100 people had been injured and 118 had been arrested during the week. One of the injured was reported on life support at a hospital but most of the injuries were minor.
A coalition of opposition groups released a statement Wednesday saying the government had used excessive force against protesters. They said the interior minister should face criminal charges and Morsi should step down.