At least three more demonstrators were killed while demanding the ruling military immediately step down, bringing the death toll to 14. More than 440 have been injured.
Protesters accuse military leaders of provoking clashes as a way to hold on to power and accuse them of using the same tactics of ousted President Hosni Mubarak.
In a nationally televised news conference, a member of the ruling military council accused the media of trying to destabilize the country.
"There is a methodical and premeditated plot to topple the state, but Egypt will not fall," said Maj. Gen. Adel Emara. "The media is helping sabotage the state. This is certain."
The criticism came hours after troops in riot gear swept through Tahrir Square, opening fire on protesters and lobbing tear gas into the crowds.
The raid appeared to be an attempt by the military to keep protesters away from key government buildings near the square, including parliament, the Cabinet headquarters and the Interior Ministry, which is in charge of the hated police.
Activists have flooded social networking sites and other media with photos and video of troops beating and attacking protesters.
Images show soldiers dragging women by the hair and ferociously beating, kicking and stomping on protesters cowering on the ground.
The Associated Press contributed to this report.