Egypt's prosecution service has referred 13 men to trial for alleged sex attacks on women at Cairo's Tahrir Square, including during inaugural celebrations for new President Abdel Fattah el-Sisi, officials have said.

The attacks took place on January 25, 2013, as Egypt marked the second anniversary of the 2011 revolt, and on June 3 and June 8 this year as locals marked Sisi's election victory and inauguration, the prosecutor general's office said on Saturday.

The 13 accused, including a minor, are charged with "kidnapping, raping, sexually attacking, attempting to murder and torturing the women", it said.

If convicted of the charges, the defendants could be sentenced to life imprisonment.

Sisi on Friday paid a visit to one of the survivors of the violence, issuing what may be the first presidential apology to a civilian and promising her to take tough actions against the attackers.

Since the uprising that toppled long-time president Hosni Mubarak in 2011, the problem of sexual harassment has worsened in Egypt, with women regularly attacked during rallies by groups of men in and around Tahrir Square, the epicentre of protests.

Widespread outrage

Activists were outraged this week after a graphic video of a woman being sexually assaulted at Tahrir Square went viral on YouTube.

Vocalising sexual harassment in Egypt

The footage, apparently filmed using a mobile phone, shows a mob of men surrounding a young woman, who was stripped of her clothes and badly bruised in the assault.

The prosecution service said police were searching for the person who recorded the video as this action was against "public morals".

Scores of Egyptians turned out for a demonstration in Cairo on Saturday demanding an end to sexual harassment.

Sabrine Abu Sabaa, a spokeswoman for the anti-harassment group Shayfenkom, said they hoped to be able to eliminate the discomfort encountered every day on Cairo's streets.

"What I am aiming for is to be able to walk on the street as a woman without feeling that I am in danger, without feeling that all the looks I'm getting are taking a part of my body," she said.

Egypt, which had no specific law on sexual harassment, only recently approved penalties for such offences to include jail terms, fines or both.

Harassers face between six months to five years in prison, with harsher sentences reserved for offenders holding a position of power over their victims, like being a woman's superior at work or being armed with a weapon.

Along with the maximum five-year sentence, offenders can be fined up to 5,000 Egyptian pounds, or about $714, with the maximum fine reserved for harassers who use a weapon or pressure.

Source: Agencies