Thousands of opponents and supporters of Egypt's Islamist president are staging rival rallies in the nation's capital, four days ahead a nationwide referendum on a contentious draft constitution.
The demonstrations got under way just hours after masked assailants set upon opposition protesters staging a sit-in at Tahrir Square, firing birdshot and swinging knives and sticks, according to security officials.
At least 11 protesters were wounded in the pre-dawn attack, according to a health ministry spokesman quoted by the official MENA news agency. The violence served as a stark reminder of the stakes in Egypt's political battle over the disputed draft constitution, which goes to a nationwide referendum on Saturday.
The referendum is likely to take place despite the head of Egypt's key association of judges saying 90% of its members have voted not to oversee the poll. Ahmed el-Zind, the chairman of the Judges' Club, announced the decision on Tuesday.
President Mohammed Morsi's deputy has said that if there are not enough judges to oversee the referendum, the vote can be staggered over several days. A faction of judges loyal to Mr Morsi has said it would not boycott the vote.
Egypt is sharply divided and polarised over the draft constitution, which was hurriedly approved by an Islamist-dominated constituent assembly despite an opposition boycott. The charter has triggered some of the worst street violence since Mr Morsi took office in June as Egypt's first freely elected president.
On one side of the divide, there is Mr Morsi, his Muslim Brotherhood and ultra-orthodox Salafis, while on the other there is a collection of liberals, leftists and Christians who claim the draft charter restricts freedoms and gives Islamists vast influence over the running of the country.
In Cairo's Nasr City district, a Muslim Brotherhood stronghold, tens of thousands of the president's backers, some of them waving Egyptian flags, rallied in front of a neighbourhood mosque.
In the nearby Heliopolis neighbourhood, tens of thousands of opposition supporters rallied outside the presidential palace, pushing their demands that Mr Morsi scrap the referendum on the charter.
With four days left before the referendum, the opposition has yet to decide whether to campaign for a "no" vote or call for a boycott - something many see as a reflection of divisions within the opposition. Anticipating unrest on the day of the referendum, Mr Morsi has ordered the military to join the police in maintaining security and protecting state institutions until after the results of the vote are announced.