A supporter of Egypt’s President Mohamed Morsi and the Muslim Brotherhood holds a copy of the Koran, Islam’s holy book, as he shouts slogans during a demonstration in Cairo’s Nasr City on December 14, 2012. / MARCO LONGARI/AFP/Getty Images

CAIRO Waving swords and clubs, Islamist supporters of Egypt’s draft constitution clashed with opponents in the Mediterranean port city of Alexandria on Friday as tempers flared on the eve of the referendum on the disputed charter — the country’s worst political crisis since the ouster of Hosni Mubarak.

Both sides stepped up their campaigns after weeks of violence and harsh divisions that have turned Saturday’s vote into a fight over Egypt’s post-revolutionary identity. Highlighting the tension that may lie ahead, nearly 120,000 army soldiers will deploy to protect polling stations. A radical Islamist group also said it will send its own members to defend the stations alongside the army and police.

The referendum pits Egypt’s newly empowered Islamists against liberals, many apolitical Christians and secular-leaning Muslims. President Mohammed Morsi’s supporters say the constitution will help end the political instability that has gripped Egypt since February 2011, when the autocratic Mubarak was overthrown in a popular uprising. Clerics, using mosque pulpits, defend the constitution as championing Islam.

Morsi’s opponents say minority concerns have been ignored and the charter is full of obscurely worded clauses that could allow Islamists to restrict civil liberties, ignore women’s rights and undermine labor unions. They charge the constitution will enslave Egyptians.

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Critics have raised concern over the legitimacy of the document after most judges said they would not supervise the vote. Rights groups warned of opportunities for widespread fraud, and the opposition said a decision to stretch the vote two rounds to make up for the shortage of judges left the door open for initial results to sway voter opinions.

Both sides of the Egyptian political divide had planned major rallies for Friday, reports CBS News correspondent Allen Pizzey. Eight people died and more than 700 were injured in violent clashes over the past two weeks, and some commentators are already warning that the country is teetering in the brink of what amounts to civil war.

The opposition coalition, the National Salvation Front, again called on Morsi, a member of the Muslim Brotherhood, to postpone the referendum and form a new assembly to draft a new constitution.