By Edmund Blair and Patrick Werr
CAIRO (Reuters) - Tens of thousands of Egyptians protested against President Mohamed Mursi on Friday after an Islamist-led assembly raced through approval of a new constitution in a bid to end a crisis over the Islamist leader's newly expanded powers.
"The people want to bring down the regime," they chanted in Tahrir Square, echoing the chants that rang out in the same place less than two years ago and brought down Hosni Mubarak.
Mursi said a 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" and aimed to speed 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 a draft, which the Islamists say reflects Egypt's new freedoms. "There is no place for dictatorship."
But the opposition cried foul. Liberals, leftists, Christians, more moderate Muslims and others had withdrawn from the assembly, saying their voices were not being heard.
Even in the mosque where Mursi said Friday prayers some opponents chanted "Mursi: void" before sympathizers surrounded him shouting in support, journalists and a security source said.
Tens of thousands gathered across the country, filling Tahrir Square and hitting the streets in Alexandria and other cities, responding to opposition calls for a big turnout. Rival demonstrators clashed after dark in Alexandria and the Nile Delta town of Al-Mahala Al-Kobra, some hurling rocks in anger.
An opposition leaflet distributed on Tahrir urged protesters in Cairo to stay overnight before Saturday's rallies by Islamists; the Muslim Brotherhood and its allies said they would avoid the square during their demonstrations backing Mursi.
The disparate opposition, which has struggled to compete with well-organized Islamists, has been drawn together and reinvigorated by the crisis. Tens of thousands had also protested on Tuesday, showing the breadth of public anger.
But Islamists have a potent political machine and the United States has looked on warily at the rising power of a group it once kept at arms length now ruling a nation that has a peace treaty with Israel and is at the heart of the Arab Spring.
Protesters said they would push for a 'no' vote in a constitutional referendum, which could happen as early as mid-December. If the new basic law were 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 Tahrir and member of a party set up by opposition figure Mohamed ElBaradei.
ElBaradei said in a statement the constitution had "lost legitimacy" and called for ending the polarization of Egypt.
The plebiscite on the constitution is a gamble based on the Islamists' belief they can mobilize voters again after winning every election held since Mubarak was toppled in February 2011.
Despite the big numbers opposed to him, Mursi can count on backing from the disciplined Brotherhood and Islamist allies, as well as many Egyptians who are simply exhausted by the turmoil.
"He just wants us to move on and not waste time in conflicts," said 33-year-old Cairo shopkeeper Abdel Nasser Marie. "Give the man a chance and Egypt a break."
But Mursi needs the cooperation of judges to oversee the vote, and many have been angered by a decree from Mursi they said undermined the judiciary. Some judges are on strike.
The assembly concluded the vote after a 19-hour session, faster than many expected, approving all 234 articles of the draft, covering presidential powers, the status of Islam, the military's role and human rights.
It introduces a presidential term limit of eight years - Mubarak served for 30. It also bring in a degree of civilian oversight over the military - though not enough for critics.
An Egyptian official said Mursi was expected to approve the document on Saturday and then has 15 days to hold a referendum.
"This is a revolutionary constitution," said Hossam el-Gheriyani, head of the assembly, urging members to campaign for the new constitution across Egypt, after the all-night session.
Critics argue it is an attempt to rush through a draft they say has been hijacked by the Muslim Brotherhood, which backed Mursi for president in a June election, and its Islamist allies.
Two people have been killed and hundreds injured in protests since the decree was announced on November 22, deepening the divide between the newly empowered Islamists and their critics.
Seeking to placate opponents, Mursi welcomed criticism but said there was no place for violence. "I am very happy that Egypt has real political opposition," he told state television.
He said Egypt needed to attract investors and tourists. The crisis threatens to derail a fragile economic recovery after two years of turmoil. Egypt is waiting for the International Monetary Fund to finalize a $4.8 billion loan to help it out.
An alliance of opposition groups pledged to keep up protests and said broader civil disobedience was possible to fight what it described as an attempt to "kidnap Egypt from its people".
Several independent newspapers said they would not publish on Tuesday in protest. One of the papers also said three private satellite channels would halt broadcasts on Wednesday.
The draft injects new Islamic references into Egypt's system of government but keeps in place an article defining "the principles of sharia" as the main source of legislation - the same phrase found in the previous constitution.
The president can declare war with parliament's approval, but only after consulting a national defense council with a heavy military and security membership. That was not in the old constitution, used when Egypt was ruled by ex-military men.
Critics highlighted other flaws, such as articles pertaining to the rights of women and freedom of speech.
A new parliamentary election cannot be held until a new constitution is passed. Egypt has been without an elected legislature since a court ordered the dissolution of the Islamist-dominated lower house in June.
(Additional reporting by Yasmine Saleh and Marwa Awad; Writing by Edmund Blair; Editing by Philippa Fletcher and Alastair Macdonald)