An Islamist-led assembly raced through approval of a new constitution for Egypt to end a crisis over President Mohamed Mursi's newly expanded powers, but opponents respond with another rally in Cairo.

Egypt constitution finalised as opposition cries foul (Reuters)

President Mursi said the decree halting court challenges to his decisions, which sparked eight days of protests and violence by Egyptians calling him a new dictator, was "for an exceptional stage", aimed at speeding up the democratic transition.

"It will end as soon as the people vote on a constitution," he told state television while the constituent assembly was still voting on the draft, which the Islamists say reflects Egypt's new freedoms. "There is no place for dictatorship."

"The people want to bring down the regime," they chanted in Tahrir Square, where hundreds had gathered, echoing the chants that rang out in the same place less than two years ago and brought down Hosni Mubarak.

The opposition cried foul. Liberals, leftists, Christians, more moderate Muslims and others had withdrawn from the assembly, saying their voices were not being heard.

They have called for a big rallies across the country on Friday after tens of thousands protested against Mursi's decree on Tuesday. Demonstrations tend to gather pace later in the day.

Degree of oversight

Protesters said they would push for a no vote in a referendum, which could happen as early as mid-December. If approved, it would immediately cancel the president's decree.

"We fundamentally reject the referendum and constituent assembly because the assembly does not represent all sections of society," said Sayed el-Erian, 43, a protester in Cairo's Tahrir Square.

He is a member of the liberal Dostour (Constitution) party, set up by prominent opposition figure Mohamed ElBaradei.

The final draft contains historic changes to Egypt's system of government. It limits to eight years the amount of time a president can serve, for example. Mubarak was in power for three decades. It also introduces a degree of oversight over the military establishment - though not enough for critics.

President Mursi is expected to ratify the document by Saturday, allowing a referendum to be held as soon as mid-December.