CAIRO (Updated) - Tens of thousands of Egyptians packed city centers across the country on Friday, demanding faster reforms and voicing frustration at what they see as foot-dragging by military rulers and government officials. Anger has been building up among ordinary Egyptians and activists against the ruling military council over what they see as delays in the prosecution of President Hosni Mubarak and former officials charged with corruption and killing demonstrators during the uprising that toppled him. Most political groups and parties including the Muslim Brotherhood, Egypt's most organised political grouping, backed calls for the protest called "The Revolution First. Cairo's Tahrir Square, the center of Egypt's uprising that toppled Mubarak in February, was decked with red, white and black Egyptian colors as tens of thousands protested in one of the biggest rallies since Mubarak's downfall. Former Arab League Secretary General, Amr Moussa, a presidential hopeful, joined the thousands of protesters at Tahrir Square, according to Egypt's news agency MENA. As with previous demonstrations since Mubarak was ousted, the thousands who gathered made political demands but were also in festive mood. Children with faces painted in the colors of the Egyptian flag joined their parents. Many Egyptians believe the repeated health problems afflicting Mubarak are a ploy by the ruling army generals to avoid bringing the decorated former air force commander to a humiliating trial. But court rulings this week clearing three former ministers of graft charges and another court's decision to free on bail 10 policemen charged with killing demonstrators sparked protests. "Punishment for the killers of the martyrs," read one banner in Tahrir Square, referring to the more than 840 people killed in the 18 days of protests Egyptians see as "martyrs." Nearby, a speaker whipped up the crowds with calls for justice. "Down with the Field Marshal," the crowd repeated after another leader on the podium. Thousands of Egyptians also gathered in other cities, including the Suez Canal cities of Suez and Ismailia, Alexandria on the Mediterranean and the Red Sea resort of Sharm El-Sheikh where Mubarak has been detained in a hospital since suffering heart problems during questioning in April. In Suez, one of the most violent spots during the uprising, sounds of gun shots were also heard and one protester was shot by a person who was caught shortly afterwards by protesters, a Reuters eyewitness said. Some protesters hurled stones at government buildings in Suez last Wednesday in response to a court decision to free 10 policemen on trial for killing protesters. "The days are passing and concerns are rising in the souls of those who love this nation about ... rooting out corruption," the Coalition of the Youth of the Revolution said in a statement. The group listed demands including calling for police officers who have used violence against protesters to be fired and the resignation of officials in the new government who have failed to deliver on their revolutionary promises. It also called for an end to trials of civilians in military courts.