CAIRO — Egyptian police on Monday arrested seven men for sexually assaulting a 19-year-old student during celebrations marking the inauguration of the country's new president in Cairo's central Tahrir Square the day before, security officials said.

Police were investigating 27 complaints of sexual harassment against women in Tahrir, where tens of thousands celebrated Abdel-Fattah el-Sissi's inauguration on Sunday late into the night, the officials said.

Sexual harassment has been one of Egypt's enduring social ills. Over the past three years, Tahrir Square has seen multiple instances of sexual attacks on women amid the large crowds that mass there for protests, rallies or celebrations ever since it became the center of the 2011 uprising that ousted autocrat Hosni Mubarak.

Last week, authorities issued a decree declaring sexual harassment a crime punishable by up to five years in prison.

The seven men were arrested in connection to an attack Sunday evening on a student, who was hospitalized afterward, said the officials. They did not elaborate on her condition and spoke on condition of anonymity because they were not authorized to speak to the media.

Video footage posted on social media purportedly shows the student completely naked amid a crowd of men, parts of her body bloodied as policemen struggle to escort her out of Tahrir. The video appeared authentic and was consistent with AP reporting of the incident.

The Interior Ministry, in charge of police, identified the seven in a statement, giving their ages between 15 and 49. It said they were arrested for "harassing several girls" but made no mention of the student. A policeman was injured while the seven were being arrested, the ministry added.

Authorities investigating other reports of sexual assaults were examining a dozen videos from security cameras or from bystanders filming with their mobile phones, the officials said.

They said the footage suggested an organized nature of harassment, with groups of young men consistently luring potential victims away from densely crowded spots before encircling them from the rest as they assault them. They said many of the harassers brandished knives which they used to threaten victims or against anyone coming to their rescue.

Further causing an uproar were comments by a TV anchorwoman during a live report by a correspondent from Tahrir during the celebration. When the correspondent for al-Nahar TV told the anchorwoman in the studio that there had been several cases of sexual harassment, the anchorwoman laughed and said it's "because they are happy."

The anchorwoman, Maha Bahnassy, denied on Monday that her comment was in response to the harassment incidents reported by the journalist.

"I was, along with my guests, commenting on people's joy, not the harassment," she said on her Facebook page.

The anti-sexual harassment decree issued last week amended Egypt's current laws on the abuse, which did not criminalize sexual harassment and only vaguely referred to such offenses as "indecent assault."

The new law says those convicted face between six months to five years in prison, with the maximum punishment reserved for offenders holding a position of power over their victims, such as when the offender is the woman's boss or is armed.

Repeat offenders would see their sentences doubled, the decree said. Along with the maximum five-year sentence, offenders can be fined up to 5,000 Egyptian pounds, or about $714.

Last year, a joint report by the United Nations Entity for Gender Equality and the Empowerment of Women, Egypt's Demographic Center and the National Planning Institute found that more than 99 percent of hundreds of women surveyed in seven of the country's 27 provinces reported experiencing some form of sexual harassment, ranging from minor harassment to rape.

The breakdown in the police force in the wake of the 2011 uprising that toppled Mubarak left the streets even more unsafe for women.

Initiatives to counter harassment also multiplied. Volunteer groups started escorting women, especially during political gatherings. Activists offered self-defense classes for women and social networking sites launched "name and shame" campaigns.