Thousands of Egyptians marched on the cabinet headquarters in central Cairo on Tuesday to demand the removal of the ruling military council.
The march, reminiscent of protests that forced former president Hosni Mubarak to step down on February 11, followed a warning by the military council that it would use all legitimate means to end a five-day-old protest in the city's Tahrir Square.
"Down, down with military rule," demonstrators chanted as they went from Tahrir Square towards the prime minister's office, where they demonstrated before returning to the square.
"The people want the removal of the field marshal," they shouted, referring to Mohammed Hussein Tantawi, the military council leader who served as Mubarak's defence minister for two decades.
The protest that began on Friday has increasingly targeted the generals running the country and is one of the longest since it took over from Mubarak following mass protests against rising prices, poverty, unemployment and years of authoritarian rule.
Protesters in Tahrir Square have blocked traffic and stopped employees entering a government administrative building on the edge of the square.
"The military council is following the same policies as the ousted regime," said Mohamed Abdel Wahed, 43, who has joined those camping in Tahrir in tents and under big white canopies.
"What protesters have been asking for consistently since the end of the revolution has been free and open trials for members of the former regime as well as policemen and police officers involved in the killing of protesters throughout that 18-day revolution," Al Jazeera's Ayman Mohyeldin, reporting from Tahrir Square, said.
"People here are extremely frustrated with the slow pace of judicial cases both the killers of protesters and the former regime," our correspondent said.
The protest and the possibility that the crisis could deepen have hit the Egyptian stock market, where the benchmark index closed down almost 3 per cent at an eight-week low.
The protesters are angry about foot-dragging in trying Mubarak, who ruled the country of 80 million people for three decades, and officials charged with corruption and killing protesters.
Other protests have been taking place in the port cities of Alexandria and Suez, where some people gathered outside a Suez Canal administration building.
Mubarak, who is at a hospital in the Red Sea resort of Sharm el-Sheikh, is due to go on trial on August 3 over the death of more than 840 protesters in the uprising.
Essam Sharaf, the prime minister, has been trying to appease the protesters by promising a cabinet reshuffle and ordering other changes in the interior ministry, but the demonstrators have rejected the proposals.
The military council said the protests were threatening public order and the country's security.
"The armed forces feels its historic responsibility and role towards the nation and calls on honourable citizens to stand against any protests that prevent the return of normal life," said a statement read by General Mohsen Fangary, a member of the military council.
The army has promised a parliamentary election in September with a presidential vote to follow.
Amr Moussa, former Arab League secretary-general and a presidential hopeful, said the protesters have legitimate demands.
"There is a gap between the revolution and the swiftness it was demanding," Moussa said.
Sharaf has promised a cabinet reshuffle within a week and on Tuesday accepted the resignation of his deputy, Yehia el-Gamal, who demonstrators had complained was ineffectual.
Earlier on Tuesday, an Egyptian court sentenced Ahmed Nazif, Egypt's former prime minister, to a one-year suspended jail term.
Two other Mubarak era ministers were also sentenced to prison for fraud, judicial sources said.