Seven suspects have been arrested in connection with the sexual assaults of at least five women in Tahrir Square during celebrations for the inauguration of Egypt's new president Abdel-Fattah el-Sisi, authorities said.
The Ministry of Interior said the men are between the ages of 15 and 49 and are being held at a local police station.
A graphic video described as showing the aftermath of an attack in Tahrir Square has been widely circulated via social media.
It shows a bloodied bruised woman stripped of her clothes and surrounded by a group of men, including a police officer, attempting to get her out of the square.
The men arrested have not been specifically linked to the attack in the video.
Local group, I Saw Sexual Harassment, which works to monitor and document sexual harassment and violence against women, said in a statement that there were at least five incidents of sexual assault in Tahrir Sunday night and that four of the victims required medical treatment as a result.
The group also condemned security efforts in the square, which it said left individuals and junior police officers to attempt to intervene and help victims. Several police were injured as a result, it added.
"It is shameful that the security leaders of the ministry of interior did not take into account any security measures or plans to prevent such incidents,” the group said in the statement.
Celebrations in Tahrir continued late into the night, undaunted by the horrific attacks.
At 3AM, there were still groups of mostly male Egyptians in the square, waving flags, letting off fireworks and releasing paper lanterns into the sky.
Separate footage showing local Tahrir TV channel anchorwoman Maha Bahnasy's response to news of the assaults provoked widespread anger.
In the video, a reporter in the square tells Bahnasy that there had been a number of harassment incidents. The anchorwoman interrupts her, laughs and says, "it is because they are happy.”
Egypt's Extreme Levels of Sexual Violence
Some said supporters of former president Mohamed Morsi and the Muslim Brotherhood, who Sisi removed from power last July, were responsible.
However, these are not isolated incidents.
The mass demonstrations which followed Mubarak's ouster (many of them anti-Morsi), saw horrifying levels of sexual violence.
In some cases, mobs of men took advantage of the lack of security forces present at these gatherings to harass, assault and even gang-rape women with impunity.
A Human Rights Watch report released last year documented extreme levels of sexual violence during protests in Tahrir.
About 99 percent of Egyptian women have faced some form of sexual harassment or assault, ranging from cat calling to rape, according to United Nations figures released last year. Activists said incidents soared in the turmoil that followed the ouster of Mubarak in 2011.
Despite the scale of the problem, sexual harassment was not formerly criminalized in Egypt until last week.
Acting president Adly Mansour finally made sexual harassment a criminal offense when he signed new legislation into law on Thursday — which will hit offenders with prison terms of between six months and five years.
The International Federation for Human Rights documented more than 250 cases of women being attacked by groups of men and boys near Tahrir Square between November 2012 and July 2013.
Not one of these incidents, it said, resulted in a prosecution.
Follow John Beck on Twitter: @JM_Beck