Thousands of flag-waving supporters and opponents of Egypt's new constitution have turned out for rival rallies, on Friday, a day before voting begins inside the country.

The measure has the support of President Mohamed Morsi's Muslim Brotherhood and ultra-orthodox Salafist groups.

However, members of liberal, secular and Christian opposition fear it will erode civil liberties because it boosts the role of Islamic law and does not mention women's rights.

A largely Islamic committee approved the document last month after liberal and Christian members walked out, complaining they were being ignored.

Last week, clashes between supporters and opponents left eight people dead and hundreds injured.

Polls open on Saturday in Cairo, Alexandria and a group of other provinces. The rest of the country will vote on December 22.

Egyptians living overseas began casting their ballots earlier this week.

Meanwhile, the United Nations Working Group has urged Egyptian officials to review the document to ensure that in conforms to international laws on equality and women's rights.

In a Friday statement, independent expert Kamala Chandrakirana said “key opportunities so far has been missed.” The group says the final draft of the constitution does not include adequate provisions to protect against gender discrimination.