Clashes erupted in Cairo on Friday after Egyptian political forces called on President Mohamed Morsy to take a stand for justice after his first 100 days in office.

Shops and streets at Tahrir Square were closed as Morsy supporters and critics threw rocks at one another. At least 121 people were injured, a spokesman for the health ministry said.

Thousands turned out for the protest, with some groups chanting, "Leave Morsy." Protesters threw Molotov cocktails at one another, and firecrackers sounded amid clashes around Tahrir and Talat Harb squares.

Witnesses said protesters from the Muslim Brotherhood attacked and destroyed a stage built by right-wing groups that criticize Morsy.

The Brotherhood said two of their buses were burned near Tahrir Square and their headquarters was burned in Mahala.

The same protesters that toppled President Hosni Mubarak in 2011 were scheduled to meet in five locations Friday and march toward Tahrir Square around 3 p.m.

"We want retribution for all the martyrs of the revolution. Those Mubarak cronies released from prison for the camel attack must return behind bars, and we also demand a drafted constitution that represents all factions in a civil democratic language," Rami Shaath told CNN, explaining the main demands of the nationwide protest.

Shaath, a founding member of the Egyptian Revolutionary Alliance, a bloc of secular and religious parties, was referring to the February 2011 "Battle of the Camel," street violence in which regime supporters, backed by men on horses and camels, attacked opposition demonstrators. He says he wants to keep Egypt's revolution going while the media covers Morsy's political maneuvers.

The acquittal Thursday of all suspects detained in relation to the battle last year has sparked a wave of discontent among youths and the Islamic movement across the country -- especially since 24 of those suspects were former senior members of Mubarak's regime.

Most of the officers charged with killing more than 800 protesters during the uprising have not been convicted.

"We also want the retrial of Mubarak, his Minister of Interior Habib El Adly and the seven chief police officers accused of killing the martyrs," Shaath said.

Many people relate the latest wave of acquittals to the removal of General Prosecutor Abdul Majid Mahmoud on Thursday night.

"The general prosecutor submitted his resignation to the president, and he appointed him as an ambassador to the Vatican," presidential spokesman Yaser Ali told CNN.

Mahmoud's removal has been a top demand during the many "million-man" protests that followed Mubarak's ouster.

In a tone of defiance, Adel Saeed, the general prosecutor's official spokesman, released a statement saying that the prosecutor has not resigned and that he will continue his business as usual, as the judicial system bans the president from firing the general prosecutor.

"He is a corrupted man appointed by Mubarak, and it would be a disgrace to the Vatican if this is true," said Mohamed Farhat, a member of the Muslim Brotherhood.

Many people who followed the revolution know the vital role the young revolutionaries took in sparking the uprising against Mubarak.

The same personalities that toppled the regime have been discreetly applying pressure by mobilizing laborers to demand more rights and better pay.

Activist Gigi Ibrahim and her husband, Hossam El-Hamalawy, a member of the Socialist movement, have supported the laborers and helped them strike against the government, including this week's action by doctors, in which people in hundreds of public hospitals took part in a partial strike and demanded higher wages. More than 30,000 people took part, the Ministry of Health said.

"If the government does not provide to the people, we may see a 'revolution of the hungry' next," Ibrahim said.