CAIRO – Mob-led sexual assaults targeting Egypt’s female protesters could increase if perpetrators are not punished, an international rights group warned on Wednesday.

Amnesty International said statements from victims show that the assaults follow a “clear pattern,” where mobs of men encircle the victims, assault them with weapons and hands and then try to undress them.

Amnesty’s warning followed a statement from the U.N. human rights office, which last week said that about 25 women were reportedly sexually assaulted — in some cases with extraordinary violence — in Cairo’s Tahrir Square during recent protests against Egypt’s Islamist President Mohammed Morsi.

The square was the center of the 2011 uprising that toppled former President Hosni Mubarak. It has been the scene of a number of assaults against women — both protesters and journalists — in the aftermath of the uprising.