Elizabeth Dickinson talks to Joe Stork from Human Rights Watch, who says that the pro-Mubarak demonstrators involved in violent clashes in Tahrir Square were explicitly sent by the government:
"These are not rival factions. This is brown-shirt tactics. This is the government sending in people -- whether they are paid or not is a very subsidiary question -- sending in thugs armed with knives, stones, sticks, to attack the pro-democracy protestors, who were there in an entirely peaceful manner."
Judging from what we're seeing in Cairo, this is one of those moments where this description doesn't seem the slightest bit hyperbolic.