Activists called for a protest on Friday and Islamists warned that the gains of the revolt that toppled Hosni Mubarak could be wiped out after Egypt's supreme court dissolved parliament and ruled to keep his last premier in this weekend's presidential race.

Protesters shout slogans against the Egyptian military council following Friday prayers in Tahrir Square, Cairo, on Friday. Egyptian parties and activists have accused the ruling military council of staging a "counter-revolution". Mohammed Abed / Agence France-Presse

Egypt's already troubled transition was plunged into turmoil by Thursday's court rulings. Islamists, who dominate parliament and have gained most since the uprising that ousted Mubarak last year, called the court ruling a "coup".

The run-off election on Saturday and Sunday was billed as the culmination of a transition before the military generals who have ruled Egypt for 16 months since Mubarak's overthrow formally hand power to a new president.

The new leader will now be elected without a parliament, whose election has been one of the few substantive gains, and without a new constitution to outline the extent of his permanent powers, a process delayed by political bickering.

Activists called for a protest march on Friday that would head to Cairo's Tahrir Square "against the soft military coup".

"We will save our revolution. We will save Egypt from military rule," the group said in a statement sent out early in the morning on Friday.

The main target of the group's opposition is presidential contender Ahmed Shafik, a former air force commander who was appointed prime minister in Mubarak's last days in office.

They fear he will seek to rebuild Mubarak's repressive state and reverse the gains of the revolt, although he denies this.

Several hundred people gathered in Tahrir Square on Thursday after the supreme court's ruling to denounce the action and rally against Shafik.

Activists who engineered Egypt's uprising have long suspected that the generals would try to cling to power, explaining that after 60 years as the nation's single most dominant institution, the military would be reluctant to surrender its authority or leave its economic empire to civilian scrutiny.

Shafik's rival in the Saturday-Sunday runoff, Mohammed Morsi of the Muslim Brotherhood, said he was unhappy about the rulings but accepted them.

"It is my duty as the future president of Egypt, God willing, to separate between the state's authorities and accept the rulings," the US-trained engineer said in a television interview. He told a news conference on Thursday: "Millions will go to the ballot boxes on Saturday and Sunday to say 'no' to the tyrants."

US Secretary of State Hillary Clinton on Thursday called for a full transfer of power in Egypt to an elected civilian government, saying "there can be no going back on the democratic transition".

"In keeping with the commitments that the Supreme Council of the Armed Forces made to the Egyptian people, we expect to see a full transfer of power to a democratically elected civilian government," Clinton said.

"There can be no going back on the democratic transition called for by the Egyptian people," she told reporters after foreign and defense ministers of the United States and South Korea concluded their talks in Washington.

"Ultimately it is up to the Egyptian people to determine their own future, and we expect this weekend's presidential election will be held in an atmosphere that is conducive to it being peaceful, fair and free," she said.

Reuters-AP-Xinhua