At least 19 people have reportedly been hurt in Egypt, after supporters of the country's draft constitution attacked protesters with swords.
The clashes in the Mediterranean city of Alexandria come on the eve of a referendum on the charter, which opponents claim does not guarantee basic rights to Egyptians and places emphasis on Islam and Sharia law.
Witnesses said dozens of protesters fought with clubs and swords and threw stones at one another.
Cars were set alight and a large crowd of anti-Mursi protesters armed with knives surrounded a mosque in the city, trapping a preacher who had criticised those planning to oppose the constitution when voting begins on Saturday.
A hospital official told the AP news agency that 19 Egyptians were injured in the clashes.
In the Egyptian capital Cairo, where tanks and armed troops have been deployed , protests outside mosques were peaceful.
Demonstrators gathered outside the presidential palace but there were no reports of any violence.
At least eight people have died and hundreds have been injured in the three weeks since Egyptian President Mohamed Morsi assumed sweeping new powers - which have now been abolished - to push through the constitution.
The referendum, which will be held on two days, asks Egyptians to accept or reject a basic law that must be in place before national elections can be held early next year.
The government said Saturday would be made a holiday to enable people to vote.