Police fear a gang-rape phenomenon known as 'taharrush gamea' in the Arab world and seen in attacks on women across German cities at the New Year has now spread to Europe.

The name of the practice translates to 'collective harassment' and is carried out by large groups of men who sexually assault lone women, either by groping, or in some instances, raping them.

The men first surround their victim in circles. Some then sexually assault her, while others not directly involved watch or divert outsiders' attention to what is occurring.

CBS reporter Lara Logan, photographed in Cairo's Tahrir Square moments before she was assaulted in 2011. Her attack was one of the first known instances of 'taharrush' to be reported in Western media

Sometimes the terrified victim - in a state of shock and unable to respond - is also robbed during the ordeal.

And the attack usually goes unpunished because the large number of perpetrators and chaos of the attack means authorities are unable to identify those involved.

There remains debate about what defines 'taharrush' - some still insist it is a reference to flirting - though scholars argue its definition changed after the attacks seen in Egypt from 2011 onwards.

German authorities have stated this was the phenomenon seen in Cologne city centre on New Year, when hundreds of women reported they were sexually assaulted.

The practice is only carried out in public and almost always at demonstrations or large public gatherings where the attackers find safety in numbers and disorder.

The Arab phenomenon first came to the attention of the Western world when South African reporter Lara Logan, working for CBS, was set upon by a large group of men while reporting on celebrations in Tahrir Square, Egypt, in 2011.

Logan recounted her ordeal in Egypt several months later on a 60 Minutes broadcast, describing how the baying crowd 'raped me with their hands'.

The 44-year-old revealed terrifying details of the 40 minute-long February attack in Cairo's Tahrir Square, including how she became separated from members of her crew after someone in the frenzied 200-strong crowd shouted 'Let's take her pants off.'

She said: 'Suddenly, before I even know what's happening, I feel hands grabbing my breasts, grabbing my crotch, grabbing me from behind. I mean, and it’s not one person and then it stops, it's like one person and another person and another person.

'And I know Ray is right there, and he's grabbing at me and screaming, "Lara hold onto me, hold onto me".'

Scholars believe that sexual assaults against women during demonstrations in Cairo were widespread following the civil disorder that erupted in Egypt in 2011

Egyptian security forces arrest a protester during clashes with demonstrators in November 2012 in Cairo

It was revealed that as she was pulled into the frenzy the camera recorded her shouting 'Stop.' It was revealed that someone in the crowd falsely shouted out that she was an Israeli Jew.

Angie Abdelmonem, a doctoral candidate at Arizona State University, recently published a study into the instances of 'taharrush' seen during the Egyptian Revolution.

She said the 'violent nature of sexual harassment and assault in Tahrir Square captured global attention', but many locally initially believed the state was hiring thugs to harass women and stem public protest.

'This [perception] shifted on February 11, the day Mubarak stepped down, with the mob assault and rape of CBS correspondent, Lara Logan,' she wrote.

'Between 2011 and 2013, sexual harassment became common at protests in Tahrir Square, exemplified by a number of highly publicized violent attacks that demonstrate how women’s bodies became objectified and dehumanized during the uprising.'

She goes on to conclude the lack of 'conceptual boundaries' of the term further blurred the lines of when acceptable flirtation became harassment.

A teenager named only as Michelle (pictured), 18, described how the New Year's Eve celebrations in Cologne a fortnight ago turned into targeted and coordinated attacks on women

The chaos outside the Cologne cathedral saw fireworks launched into the crowd and hordes of drunk Arab or North African men assaulting women, German police said

Leaked police reports later emerged showing officers were unable to stop the disorder and they were swamped by upset women at the scene claiming they had been sexually assaulted

A reveler lets off a firework in Cologne city centre during the chaotic celebrations on New Year's Eve

German police believe it was 'taharrush' committed in Cologne and other cities at New Year by Arab and North African men that led to hundreds of police complaints in the following weeks.

German federal police told Die Welt that crimes are committed by groups of young men during large gatherings of people, such as demonstrations, and range from sexual harassment to rape.

It was the first instance of the phenomenon having reached Europe, and as the scale of the attacks in the city slowly emerged, other centres, such as Zurich and Salzburg, reported similar crimes.

A report from the Interior Ministry in North Rhine-Wesphalia (NRW) state, where Cologne lies, said 516 criminal complaints had been registered, 237 of which were of a sexual nature.

A separate report from the Cologne police gave graphic descriptions of the crimes, listing case after case of women surrounded by gangs of men who put their hands in the victims' pants and skirts, grabbed them between the legs, on the buttocks and the breasts, often while stealing their wallets and cell phones.