Tens of thousands of Egyptians waved flags and shouted slogans in Cairo's central Tahrir Square, demanding that Hosni Mubarak and his family be put on trial over allegations of corruption.
The demonstration was one of the biggest protests since the long-time president was ousted two months ago. The massive turnout reflected growing frustration with what activists see as the slowness of Egypt's new military rulers to punish former senior figures in Mubarak's regime seen as using their power to amass personal fortunes.
The military appears to be trying to accelerate the prosecutions, with authorities announcing on Thursday that Mubarak's former chief of staff, Zakariya Azmi, had been detained for questioning on corruption allegations, the highest-ranking member of his regime to be arrested so far.
They also said investigators would begin questioning another senior regime insider, former ruling party chief Safwat el-Sharif.
Since his removal on February 11, Mubarak and his family have been under house arrest at a presidential palace in the Red Sea resort of Sharm el-Sheikh, with their assets frozen.
The crowds packing Tahrir Square chanted to defence minister Field Marshall Hussein Tantawi, who heads the military council that now runs the country, demanding prosecutors go after Mubarak and his sons - including Gamal, an investment banker-turned-politician who was seen as Mubarak's choice as his successor.
Organisers labelled the protest "Friday of Purification and Trial", referring to the demand to cleanse the government of corruption. Protesters put together a makeshift cage on the pavement in Tahrir, with pictures of Mubarak and his family inside.
Since Mubarak's fall, the unprecedented youth movement that ousted him has seen some fragmentation, as the military pushed ahead with a quick timetable for new parliament and presidential elections to be held in September and November. That has sent various factions scrambling to get organised to contest the vote.
But the corruption issue provides a unifying theme that resonates among most Egyptians. Mubarak's regime was long criticised as deeply corrupt - particularly a group of millionaire businessmen-politicians close to Gamal who many believe profited from their positions as Gamal implemented a programme of economic privatisation and liberalisation.
Many Egyptians also want to see the leadership punished for years of political repression, including widespread vote fraud during elections and security crackdowns. Already, a string of former officials have been put on trial or under investigation.