George Isaac, a prominent member of the Kifaya (Enough) pro-reform movement, on Friday lambasted official poll results, accusing the government of manipulating ballots.
"There was a bus full of voters that was seen visiting several electoral districts casting multiple votes," he said.
A number of government employees were provided free transportation to polling stations.
The Interior Ministry had earlier announced that 82.86% of 17.18 million voters who participated in the referendum approved the amendment to Article 76 of the national constitution, while 17.14% voted 'no'.
The amendment, which President Hosni Mubarak formally approved on Friday, will introduce the country's first direct and contested presidential elections.
Aljazeera has reported quoting Egyptian police that 77 students from the banned Muslim Brotherhood were freed on Saturday on the orders of the attorney-general.
The students had been arrested in recent weeks as part of the government crackdown on the pro-reform demonstrations by the banned but tolerated group.
The Egyptian government had announced in the days preceding the referendum that it would provide buses for all public sector employees to and from polling stations.
President Hosni Mubarak has
approved the referendum results
"How can we trust the results of the referendum with such irregularities taking place?" Isaac said in an interview on Aljazeera.net.
The government did admit in a Ministry of Interior statement that it had annulled more than 787,000 votes, which it described as faulty, but did not provide further details.
Voter turnout was said to be 53.6%, but some questioned the figure.
"This is a number that has never been reached in any previous election in the country," said Diaa Rashwan of the Al-Ahram Centre for Strategic and Political Research.
Rashwan said the government might have fumbled when it declared that the 53.6% figure was the highest turnout in any election or referendum, contradicting voter turnout figures of more than 90% in previous elections.
But the government brushed aside criticism, calling the referendum, voter turnout and results great successes representing "the powerful response of the people to those calling for a boycott of a national duty" even before official results were announced on Thursday evening.
"This unprecedented enthusiasm for participating in the referendum to amend the constitution is a decisive response from the people who want to practise their political rights," chief editor Galal Doueidar wrote in the semi-official Al-Akhbar newspaper's Thursday afternoon edition.
The government described the
referendum as a great success
Ibrahim Nafie, editor-in-chief of the pro-government Al-Ahram newspaper, said the results herald a new phase of national progress.
"By approving the amendment to Article 76 proposed by the Shura Council and People's Assembly, Egyptians have confirmed with unwavering clarity that they want to continue the political reform process," he wrote in Al-Ahram's Friday afternoon edition.
Ayman Nour, head of the Al-Ghad (Tomorrow) opposition party, disagreed.
"If this is to going to be a sampling of what will happen in the upcoming presidential elections, I can say that we will experience the worst presidential elections in Egypt's history," he told Aljazeera.net.
"This is a bad way to start what they call reform."
But many Egyptians on Friday evening turned their focus to the possibility that some of the female opposition members demonstrating against the referendum had been sexually assaulted.
"This is a bad way to start what they call reform."
leader of the Al-Ghad Party
On Thursday and Friday, several Kifaya officials accused the government's security forces of negligence after female members of the group were allegedly assaulted by government supporters.
Rabaa Fahmi said she was attacked and had her clothes torn as she marched in a demonstration that the Interior Ministry had warned against.
"When they saw that I was wearing a Kifaya badge, they [government supporters] attacked me and groped me in inappropriate places on my body," she said.
Fahmi said that with help from other demonstrators she managed to apprehend the person who assaulted her and hand him over to security forces at the march.
"Security personnel told me to go home, but I refused to leave," she said.
However, Fuad Allam, a former senior official in Egypt's security apparatus and currently a security expert for the government, disputes accounts of sexual assault.
Security officials denied any
women were sexually assaulted
"Yes, there were clashes between the security men and people from Kifaya, but what they have alleged about women being harassed is nonsense. If it was true, why didn't they go to the police station and file a complaint or charge?"
When asked if she had reported the incident to the police and filed charges, Fahmi would only say that her alleged assailant was led out of the area where demonstrators had gathered and apparently released.
Late on Friday evening, Abdullah El Senawi, editor-in-chief of the Al Arabi newspaper, called on the government to investigate the sexual assault allegations.
"It is a crime that should not simply be overlooked," El Senawi said.
"The head of the Shura Council, as well as the minister of interior, Habib al-Adly, should be questioned about what happened," he added.