Violent clashes broke out Thursday between Egyptian riot police and demonstrators supporting two pro-reform judges who accused the judiciary of helping to rig last year's parliamentary elections.
Several hundred protestors from the Muslim Brotherhood, the Kefaya movement and other leftist organisations gathered in downtown Cairo and were surrounded by thousands of policemen.
Riot police were seen beating up protestors with truncheons.
"Dozens of members of the Muslim Brothers were arrested," said spokesman Issam al-Aryan, whose Islamist opposition movement was for the first time taking part in a demonstration of support for the judges.
Large sections of central Cairo were sealed off to traffic as the political opposition and reformists faced off with state security forces.
"Judges, protect us from dictatorship," chanted the protestors, who split into at least three separate demonstrations in a bid to avoid being encircled by the police.
An AFP reporter saw one protestor lying on the ground being kicked in the stomach by policemen and several others with bloodied faces being whisked away in police vans.
Several journalists were also manhandled by security, including a cameraman for Al-Jazeera who was badly beaten and had his equipment briefly confiscated, witnesses told AFP.
A cameraman and sound engineer for state-owned Qatari television were arrested while covering the protests, their Cairo bureau said.
And another cameraman for Turkish television was roughed up and his equipment commandeered, witnesses said.
Abeer al-Askari, a journalist for the independent Al-Destour newspaper, also said she was detained briefly at a Cairo police station, beaten, kicked and sexually harassed by policemen.
Security forces sealed off Cairo University's campus after lecturers staged a protest in support of the judges, preventing them from joining other demonstrators downtown.
Mohammed Abdel Quddus, a prominent member of the journalists syndicate's board, was arrested early Thursday at a cafe near the courthouse.
The two rebel judges, Mahmud Mekki and Hisham al-Bastawissi, refused to enter the courtroom, where their case was supposed to be reviewed, claiming that their defence team was not allowed to come with them.
"I will no longer attend the hearings of the disciplinary board if the conditions for a fair trial are not met," Bastawissi told AFP.
The hearing went ahead without the pair, who demanded that their lawyers be allowed in, that all security forces vacate the building and that all protestors detained for supporting them be released. The trial was adjourned until next Thursday.
"What is happening today is an unprecedented scandal. The judges all refused to enter the courthouse, which is besieged by thousands of police forces who are interfering with the country's judiciary," Bastawissi added.
The two judges were summoned to a disciplinary hearing last month on charges of tarnishing the image of the judiciary by naming some of their pro-government colleagues in connection with election fraud.
Their summons triggered street protests in favour of the judges, who are in charge of supervising the electoral process and have become one of the symbols of the drive for reforms in Egypt.
Clashes between police and the protestors also erupted at the previous hearing on April 27 but the protestors were fewer in number.
According to Human Rights Watch, more than 100 pro-reform activists have been detained over the past two weeks in connection with the movement to support the judges and the campaign to repeal Egypt's state of emergency law, which has been in place since 1981.
Witnesses said security forces arrested more protestors on Thursday, but it was not immediately clear how many.