CAIRO (AFP) - Protesters loyal to ousted Islamist president Mohamed Mursi clashed with police Friday as Egypt awaited official results of a constitutional referendum the army-backed government billed as an endorsement of Mr Mursi's overthrow.

Clashes were reported in Cairo and the Suez Canal city of Ismailiya, while police fired tear gas to disperse a demonstration in Suez itself, security officials said.

The interim authorities trumpeted the two-day poll as a chance for voters to show their support for the army's overthrow of Egypt's first freely elected president last July after mass protests on the streets.

Flagship state-owned daily Al-Ahram hailed a 98 percent vote in support of the new charter drawn up the interim authorities to replace the Islamist-inspired one adopted under Mr Mursi's rule in December 2012.

Mr Mursi's Islamist supporters, who boycotted the vote, described it as a farce and predicted it would culminate in the sort of massive electoral fraud that characterised the three-decade rule of Hosni Mubarak, ended by the Arab Spring uprising of 2011.

Police fired tear gas at pro-Mr Mursi protesers in Cairo and the Mediterranean city of Alexandria, security officials and state media said, in what has become a weekly ritual in a massive crackdown on Islamist protests.

The government hoped a large turnout among Egypt's 53 million registered voters in the referendum would shore up its democratic credentials and further marginalise the Islamists.

Army chief Abdel Fattah al-Sisi, the man who toppled Mr Mursi, was closely monitoring voter participation as an indication of support for a presidential bid later this year, military officials said.

Preliminary tallies reported by the state MENA news agency suggested turnout had reached 39 percent in most provinces in the two days of polling on Tuesday and Wednesday, sharply up on the 33 percent registered in the Mr Mursi-era referendum just over a year ago.

The office of interim president Adly Mansour hailed a "high turnout" in the vote on a new charter it says gives new protections for free speech and women's rights, although it gave no figures.

The government said the vote showed support for Mr Mursi's overthrow. "This was also a referendum on June 30," said government spokesman Hany Salah, referring to the day when millions of protesters took to the streets demanding Mr Mursi's resignation.

But the Islamist opposition mocked the figures put out by state media and called for mass demonstrations on Saturday of next week, the third anniversary of Mr Mubarak's overthrow, to protest what they charged was a return to the mockery of democracy that characterised his rule.

"Let the putschists deceive themselves and hold fools' celebrations," it said.

"The whole world laughs at them as they bring back six decades' corruption and fraud, and the usual 99.99 per cent results in all elections, in their favour - of course."