By Yasmine Saleh and Marwa Awad
CAIRO (Reuters) - Egyptians flocked to the polls on Saturday for the first time since President Hosni Mubarak was toppled to vote in a referendum on political reform marred by an attack on presidential candidate Mohamed ElBaradei.
Youths pushed and hurled missiles at the former head of the U.N. nuclear watchdog as he tried to vote in the constitutional referendum which will determine how quickly Egypt can hold elections.
"We don't want you, we don't want you," chanted the crowd of about 60, many of them teenagers.
"I went to vote with my family and I was attacked by organized thugs," ElBaradei wrote on Twitter. "Top figures of Mubarak's regime still at large and undermining the revolution," he said.
Rocks thrown at ElBaradei's car smashed its rear window as he fled the crowd, a Reuters witness said. He was unable to vote at the Cairo polling station and went elsewhere to cast his ballot.
"They came out of nowhere. They were not in line to vote. They started chanting in unison 'We don't want you' all of a sudden. It looks like it was coordinated," said Sameh Fathi, 25, who had been waiting in line to vote.
Observers said there appeared to have been an unprecedented turnout for the first Egyptian ballot in living memory whose outcome was not known in advance.
"I'm 53 and I have never voted before because they were all rigged," said Ahmed al-Hami, one of close to 100 people waiting in line to vote at a polling station in a suburb south of Cairo. "Now I am voting for freedom," he said.
Voters were being asked to approve or reject proposed reforms drafted by a judicial committee appointed by the country's military rulers, who have pledged to hold early elections.
They took power from Mubarak when he was forced from office on February 11 by an uprising that continues to reverberate across the Arab world.
The referendum has divided Egyptians between those who say the constitution needs to be completely rewritten and others who argue amendments will suffice for now.
"Judging from what I saw in many stations, the turnout will range between 60 and 70 percent which is unprecedented," Gamal Eid, a monitor, said. "We have not seen any forgery today. What we saw was a true will to make the voting process fair."
The Muslim Brotherhood, a well organized Islamist group, has backed the amendments, setting it at odds with secular groups and reform advocates including ElBaradei and Arab League chief Amr Moussa, who is also a presidential candidate.
Remnants of Mubarak's National Democratic Party (NDP) have also said they support the amendments. Reformists see members of the party as one threat to the deep changes they are seeking.
MILESTONE ON ROAD TO ELECTIONS
Constitutional reform is a milestone on the path sketched by the military toward legislative and presidential elections that will allow it to hand power to a civilian, elected government.
The military, eager to relinquish power as soon as possible, has indicated that parliamentary elections could happen as soon as September, to be followed by a presidential election.
Rejection of the amendments would upset their plans. A security source said that under such a scenario, the parliamentary election could be pushed back to December.
One of the reforms limits the time a president can stay in office to two four-year terms -- a dramatic departure from the system that allowed Mubarak to stay in office for 30 years.
"I voted yes -- yes for stability and for things to go back to normal," said Mustafa Fouad, 24, an engineer voting in Cairo at a polling station.
"I voted no. This is not enough," said Atef Farouk, who arrived at the same polling station with his wife and three daughters. They waved an Egyptian flag as their parents voted.
"We want a new constitution," added Farouk, 41.
The result is expected to be announced on Sunday evening or Monday morning, a member of a judicial committee involved in overseeing the election told Reuters.
Voters emerged from the polling stations bearing ink-stained fingers as proof they had cast their ballots.
The Muslim Brotherhood was banned under Mubarak but has become more prominent in public life since he was toppled, making the most of new freedom to organize and speak out. The group has said it will neither seek the presidency nor a parliamentary majority in the coming elections.
Secular groups are worried that what they see as a tight timetable for elections will play into the hands of the Brotherhood and remnants of Mubarak's NDP.
Both have more political experience than other groups emerging from years of oppression under Mubarak.
(Additional reporting by Dina Zayed, Jonathan Wright, Shaimaa Fayed, Sarah Mikhail in Cairo; Abdel Rahman Youssef in Alexandria and Yusri Mohamed in Ismailia; Writing by Tom Perry; editing by Mark Trevelyan and David Cowell)