Clashes have erupted in Alexandria in front of the Qaed Ibrahim mosque and along the nearby corniche between several thousand opponents and supporters of the draft constitution.
The fight extended to the surrounding Azareeta neighbourhood with anti and pro constitution groups exchange slogans and rock throwing.
Stones are being exchanged between the two groups and cars parked on the corniche have been torched. Central Security Forces (CSF) are attempting to end the fighting.
A member of the CSF told Ahram Online that four bearded men had been arrested carrying knives.
Ahram Online's Randa Ali says she saw security forces confiscating knives from a bearded man with an injured head before arresting him.
Fighting erupted following Friday prayers at the Qaed Ibrahim mosque where prominent preacher Ahmed El-Mahalawy had urged worshippers to vote 'Yes' in the constitutional referendum on Saturday, stating it would bring stability.
A man with his head wrapped in bandages, told Ahram Online that after the preacher's statement he had started chanting "down with the rule of the Supreme Guide" from inside the mosque. Five sheikhs then beat him up and two of his friends were being detained inside the mosque by members of the Muslim Brotherhood.
The early skirmishes halted then erupted again when anti-constitution protesters were attacked by bearded men, an eyewitness told Ahram Online. Many knives were found inside the men's cars so protesters set the cars on fire, the eyewitness added.
Nine people were killed and hundreds were injured last week during clashes between supporters and opponents of President Morsi and the draft constitution.
Half the country will vote on the constitution on 15 December, the second half a week later on 22 December.