ALEXANDRIA, Egypt (Reuters) – Police fired teargas on Friday when supporters of Egyptian President Mohamed Morsi and his opponents hurled stones at each other in Egypt’s second city on the eve of a vote on a new constitution shaped by Islamists, a Reuters witness said.

Dozens of opponents of the new constitution and thousands of Islamists, separated by several lines of riot police, hurled rocks over the security cordon at each other near a mosque in Alexandria that was the focus for violence last week.

“God is great,” Islamists chanted when the stone-throwing began.

Thousands of chanting Islamists rallied on Friday in support of an Islamic vision of Egypt’s future on the eve of a constitutional referendum that has divided the most populous Arab nation.

The Muslim Brotherhood called for the mass gathering in Alexandria to protest after a violent confrontation between Islamists and the liberal, secular opposition last week ended with a Muslim preacher besieged inside his mosque for 14 hours. Rival factions had used clubs, knives and swords.