Taharrush jamai

Scene in front of Cologne Cathedral on New Year's Eve, when over a hundred women were assaulted allegedly by "immigrants".

From an article in Wikipedia:

The mass sexual assault of women in public has been documented in Egypt since 2005. Egyptian security forces and their agents were blamed for using it during political demonstrations in Tahrir Square, Cairo, as a weapon against female protesters. The behavior spread, and by 2012 sexual assault by crowds of young men was regularly seen at protests and religious festivals in Egypt.

Typically acting under the protective cover of large gatherings, assailants encircle a woman while outer rings of men deter rescuers. The attackers may pretend to be there to help, adding to the confusion. Activists have called this "circle of hell," in which women have reported being groped, stripped, beaten, bitten, penetrated with fingers and raped.

Commentators say the attacks reflect a misogynist ideology that blames women for leaving the house, seeks to terrorize them out of public life, and views sexual violence as a source of shame for the victim, not the attacker.

Difficult to believe that this practice is condoned by the imams, but you never know these days. At least one imam is reported as saying that he was not surprised that women were assaulted in Cologne. He used the "they were asking for it" argument.