A number of prominent human rights groups have called for a re-run of the first phase of Egypt's constitutional referendum due to numerous violations reported during polling on Saturday.

"Despite the revolution, we had a referendum like those held during the Mubarak era," Cairo Institute for Human Rights Studies (CIHRS) leader Bahi El-Din Hassan said at a press conference on Sunday.

Hassan went on to list several types of violations that "invalidate the whole [referendum] process."

For example, there were cases of 'fake' judges overseeing the voting at polling stations.

He also accused several judges of closing polling stations early despite an order by the Supreme Electoral Commission (SEC) to extend voting until 11pm.

Human rights lawyer Negad El-Borai added that members of civil society organisations were banned from entering polling stations. However, members the Freedom and Justice Party were given permits to enter polling stations and sometimes used that access to encourage people to vote 'Yes'.

"We have reported all the violations, but there has been no response from the SEC," added El-Borai, who questioned how the SEC could release statements denying violations had occurred without investigating them.

El-Borai added that the violations were serious enough to invalidate the referendum and reminded both Hossam El-Gheriany and Ahmed Mekki, who were part of the Judges intifada of 2005, that they had earlier said any "flaw" in the electoral process made it invalid.

Judge El-Gheriany was head of the Constituent Assembly that drafted the constitution, while Judge Mekki was appointed justice minister by President Mohamed Morsi on 12 August.

Furthermore, El-Borai accused El-Gheriany, who also heads the National Council for Human Rights, of giving more than 20,000 election-monitoring permits to members of the Freedom and Justice Party.

"It is for the commission's own good to admit its failure to properly organise the referendum and to call for a re-run," he said.

El-Borai asserted that no matter what the result was, the referendum should be void.

Human rights lawyer and Shayfenkom (We are watching you) member Ragia Omran said the group's hotline had received thousands of calls about violations during the referendum.

"More than 3,000 reports of violations were filed by citizens, not from monitors," said Omran, who added that many police reports were filed to complain about the lack of judges inside polling stations.

A protest organised by Shayfenkom will take place on Sunday at 8pm in front of the SEC headquarters to denounce the polling violations.

Meanwhile, Appropriate Communication Techniques for Development (ACT) director Azza Kamel said her group had received around 4,000 reports of violations, including 1,400 official reports about "huge violations."

Kamel also complained of "deliberate delays" at women's voting stations, especially in Cairo and Alexandria, aimed at hindering voters.

All the activists and lawyers present at the press conference demanded a re-run of the first phase of the referendum, saying further action would be decided upon after a response had been received from the SEC.

Those present said complaints would be sent to the prosecutor-general and demanded the justice minister form a delegation of judges to investigate reports of violations as soon as possible.

"The manipulation of the people's will did not start [on Saturday]; it started with the formation of a Constituent Assembly dominated by one current," CIHRS leader Bahi El-Din Hassan added.

Almost half of Egypt's governorates voted on the constitution on Saturday. Preliminary results suggest 56.5 per cent voted 'Yes'.

The second phase of the referendum is scheduled to take place on 22 December.