Egyptians are to start deciding Saturday whether to adopt a new constitution backed by Islamists including President Mohamed Morsi, or reject it as urged by the opposition which fears it will usher in sharia-style laws.

Weeks of protests and violent clashes between rival camps that left eight people dead last week have failed to dissuade Morsi from holding the referendum, which will be staggered over a week.Voters in the biggest cities of Cairo and Alexandria and eight other governorates will cast their ballots on Saturday. A week later, on December 22, the other half of the country will go to the polls.

Morsi ordered the split vote because many judges are refusing to oversee the plebiscite in protest.Islamists backing Morsi and the secular opposition ranged against them began campaigning in earnest on Thursday."It's you who will pay the price if you vote yes. No to the constitution," said an online campaign advertisement by an opposition group called April 6.

The pro-referendum camp released videos with a song whose lyrics say: "This constitution is not too bad, it was written by a committee of heroes."It also has supporters holding "Yes to the constitution" placards along main roads.

The largely secular and liberal opposition sees the draft constitution drawn up by a panel dominated by Islamists as weakening human rights, the rights of women and the independence of judges.It fears Morsi and the Muslim Brotherhood together with ultra-orthodox Salafists want to push Egypt towards an Islamic state under a form of sharia, or Islamic law.

The opposition umbrella group the National Salvation Front is urging a "no" vote -- but also says it may yet call a boycott by its supporters if the referendum is not "transparent".The coalition has demanded the referendum be held over a single day and that judges and independent foreign monitors watch over every polling station.

Morsi's camp says it is up to Egypt's 32 million voters to decide the referendum.It argues the constitution will bring stability to a country that is trying to establish democracy after last year toppling the 30-year regime of president Hosni Mubarak.

The powerful army, which is maintaining a neutral role, has been given powers of arrest up to the time results of the referendum are released to help police maintain order.A total of 130,000 police and 120,000 soldiers will be deployed on Saturday to provide security, interior ministry and military officials told.

Analysts said the proven ability of the Muslim Brotherhood to promote its views at the ballot box could well see the draft constitution adopted, though that was not certain.