Foreign journalists have been beaten with sticks by pro-government mobs and dozens detained by security forces, reports say.
The US condemned what it called the “systematic targeting” of the reporters, photographers and film crews who have brought searing images of Egyptian protests to the world.
Foreign photographers reported attacks by supporters of president Hosni Mubarak near Tahrir Square, the scene of vicious battles between Mubarak supporters and protesters demanding he step down after nearly 30 years in power.
The Egyptian government has accused media outlets of being sympathetic to protesters who want Mubarak to quit now rather than complete his term as he has pledged.
Among the many detained were correspondents for The New York Times, Washington Post and Al-Jazeera. Human rights groups said many activists were taken away after a raid by the military police on a legal centre in Cairo.
Press Association photographer Lewis Whyld, who has travelled to Egypt to cover the protests, said he was attacked by pro-Mubarak supporters while he was trying to take images of the chaos which unfolded throughout the day.
“This is a dark day for Egypt and a dark day for journalism,” said Joel Simon, executive director of the Committee to Protect Journalists. “Egypt is seeking to create an information vacuum that puts it in the company of the world’s worst oppressors.”
CPJ said some state-owned television and private stations owned by businessmen loyal to Mubarak had been portraying journalists as part of plots to destabilise Egypt.
Earlier Egypt’s prime minister apologised for an attack by supporters of his regime on anti-government protesters in central Cairo – and vowed to investigate who was behind it. The protesters accuse the regime of sending a force of paid thugs and policemen in civilian clothes to attack them with rocks, sticks and firebombs.
Prime minister Ahmed Shafiq told state TV: “I offer my apology for everything that happened yesterday because it’s neither logical nor rational.” Mr Shafiq called the attack a “blatant mistake” and promised to investigate “so everyone knows who was behind it”.