ALEXANDRIA, Egypt -- Violence erupted between Egypt's divided camps on Friday, the eve of the final round of a referendum on a constitution that has polarized the nation, as Islamists and their opponents pelted each other with stones while police fired tear gas in the streets of the Mediterranean city of Alexandria.

The contentious referendum, which would bring a greater implementation of Islamic law to Egypt, is expected to be approved in Saturday's voting.

The new clashes -- in which opponents of Islamists set fire to cars and dozens of people were hurt -- illustrated how the new charter is unlikely to ease the violent conflict over the country's future. For a month, Egypt has been torn between Islamists and their opponents, who accuse President Mohammed Morsi and his Muslim Brotherhood of trying to unilaterally impose their will on the country.

Meanwhile, Morsi was already gearing up for the next steps after the constitution's passage, making a last-minute appointment of 90 new members to the parliament's upper house, a third of its total membership. Current rules allow him to do so, but if he waited until the charter was passed he could only appoint 10.

The body is normally so toothless and ignored that few Egyptians bothered to vote in elections for it earlier this year, allowing an almost total sweep by the Brotherhood and other Islamists. But once the charter is passed, it will hold lawmaking powers until elections for a new lower house are held -- not expected for several months.

Friday's appointments added to the tiny ranks of non-Islamists in the upper house, known as the Shura Council, but preserved the Islamists' overwhelming hold.

A spokesman for the main opposition umbrella National Salvation Front dismissed the appointments, accusing Morsi of setting up a token opposition much like ousted autocrat Hosni Mubarak did.

"This council and this constitution will also fail as long as there is no real opposition and no real dialogue, and as long as Morsi is only serving his clan and taking orders from the head office of the Muslim Brotherhood," Hussein Abdel-Razek told The Associated Press.

For the past month, both sides have been bringing their supporters into the street for mass rallies sometimes numbering in the tens of thousands -- and repeatedly erupting into clashes.

In part, Egypt's split has been over who will shape the country's path two years after Mubarak's ouster. An opposition made up of liberals, leftists, secular Egyptians and a swath of the public angered over Morsi's 6-month-old rule fear Islamists are creating a new Mubarak-style autocracy. They accuse the Brotherhood of monopolizing the levers of power and point to the draft charter, which Islamists on the Constituent Assembly rammed through despite a boycott by liberal and secular members.

Morsi's allies say the opposition is trying to use the streets to overturn their victories at the ballot box over the past two years. They also accuse the opposition of carrying out a conspiracy by former members of Mubarak's regime to regain power.

Intertwined with that is a fight over Islam's role in the state. Many Islamists vow to defend God's law, and clerics have depicted opponents as infidels. The constitution would give broad leeway for hard-liners to implement Islamic Shariah law, making civil liberties and rights of women subordinate to a more literal version of Islamic law. It also gives clerics a say in legislation for the first time to ensure parliament adheres to Shariah.

Passage of the charter will do little to resolve the confrontation -- particularly if it is approved by a low margin with little turnout. The first round of voting took place Dec. 15 in 10 of Egypt's 27 provinces, and preliminary results showed a meagre 32 per cent turnout, leading to a 56 per cent "yes" vote.

Voting Saturday will take place in the remaining 17 provinces. Preliminary results are likely to be known late Saturday or early Sunday.

Top opposition figure Mohamed ElBaradei urged the public to vote "no," saying, "We know if this constitution is passed, there will be no stability."

"This is not the road for stability or democracy," he said in a speech aired Thursday night. "When 45 per cent of people say 'no,' it is a strong indication. Some don't read or write, but they are conscious that they should not be tricked."

The violence in Alexandria was a sign of how the conflict has moved beyond the issue of the constitution, to the deep resentments between the two camps.

Riot police swung batons and fired volleys of tear gas to separate stone-throwing Brotherhood members and ultraconservative Salafis on one side, and youthful secular protesters on the other.

The clashes started when the two groups met just after Friday prayers at the city's main Qaed Ibrahim mosque, by the coastal promenade. Throngs of Salafi Islamists, most wearing the long beards favoured by the movement, had gathered there for what they called "a rally to defend clerics and mosques." Waving black Islamic banners, some chanted "God is Great!" and warned opponents: "With blood and soul, we redeem Islam."

It was unclear who started the fight. During the battles, secular youths set fire to two buses and two cars belonging to Islamists, sending thick black smoke through the upscale city centre. Under a heavy cloud of tear gas, the two sides pulled back, but then continued fighting for hours past dusk along the corniche, near the famed Alexandria Library.

At least 42 people were treated for injuries, with some rushed to the hospital, a city health official said.

The Islamists' rally was called in response to violence last week, when a well-known Salafi cleric in Alexandria, Sheik Ahmed el-Mahalawi, was trapped inside a mosque for 12 hours while his supporters battled stone-throwing opponents outside with swords and firebombs.

El-Mahalawi, 87, had stirred anger with a sermon in which he denounced opponents of the draft charter as "followers of heretics."

In a further sign of the tensions opened up by the crisis, the Brotherhood in Alexandria accused the security forces of conspiring with "thugs" loyal to ElBaradei's Dustour Party and other liberal groups that it claimed attacked the Islamists in Alexandria.

"There was clear collusion by the security forces, which did nothing (to stop the attackers)," said Anas al-Qadi, a Brotherhood spokesman in Alexandria, according to the website of the Brotherhood's political party.

"In whose interest are the Interior Ministry and the governorate's security director working?"

Egypt's security forces have been divided by the country's turmoil, with some police in the streets showing support for anti-Morsi protesters, while others are believed to be backing the president. The crisis' worst violence came on Dec. 5, when Brotherhood supporters attacked an opposition sit-in outside the presidential palace in Cairo, and the ensuing violence left at least 10 dead and hundreds injured on both sides.