WARSAW (Reuters) - Magdalena Sroda, a Polish feminist and academic, was about to deliver a lecture at Warsaw university on "Morality in public life," when around 50 young men wearing balaclavas and plastic animal masks shoved their way into the building.
Security guards pushed them from the auditorium and they moved to an adjacent hall, waving fists and shouting a chant from the soccer terraces that compares opponents with Poland's widely despised former Soviet overlords:
"Hit the red trash with a hammer, with a sickle!".
They soon dispersed and the lecture went ahead, but the audience, which included professors and two university deans, was shaken, Sroda told Reuters, recalling the incident in February, one of a growing number since late last year.
"We are dealing with a new political movement that has decided to use barbarity against democracy," she said.
The invasion by "flash mobs" of liberal lectures and conferences marks a new battleground in a years-long struggle between Poles seeking to embrace liberal, western European values and those who say phenomena like feminism and gay partnerships are a corruption of traditional Polish values.
The masked gangs are loosely affiliated to far-right groups and have targeted, among others, the editor of a major newspaper, the first openly gay member of parliament and a student society planning to debate same sex couples.
They coincide with a rise of the far-right in countries across Europe as recession bites. Hungary's far-right Jobbik party is now third biggest in parliament, while in Greece, the far-right Golden Dawn won 7 percent of votes last year.
In Poland, where the far right is not in parliament, the "flash mobs" combine elements of both ends of the right-wing spectrum. At one is the hooliganism of the soccer fans who fight police with their club scarves over their faces and whose anti-communist chants can mask anti-Semitism and homophobia.
At the other is the organization and social conservatism of the mainstream right-wing, which expresses its views in parliament, Catholic sermons and on television talk shows.
Together, they make a potentially explosive mix.
"Football fans are the avant-garde of the young generation today," said Artur Zawisza, a former member of parliament who is now one of the leaders of the National Movement (Ruch Narodowy), which aims to unite the forces of Poland's far-right.
The "flash mobs" were well-organized groups standing up for their beliefs, Zawisza said, adding that he had nothing to do with inspiring or organizing them but understood their frustration with the liberal establishment.
"There are so many examples of disregard for Polishness, for tradition, history and culture that it causes anger and rebellion."
Poland's far-right agenda ranges from fighting social liberalism and rights for sexual minorities to calls for the creation of a Catholic state for the Polish nation.
Even in the political mainstream, conservatism is strong. The legislature in January threw out draft laws aimed at giving homosexual couples limited legal rights and deputy Krystyna Pawlowicz of the largest opposition party, Law and Justice (PiS), said gay people should attend "therapy centers".
The mobs have yet to affect policy, but many intellectuals say they have a chilling effect on academic debate; at least one university discussion has been canceled because organizers feared it could be hijacked by far-right activists.
Prime Minister Donald Tusk condemned the flash mobs after the incident at Warsaw university. "If we do not act in an unambiguous way, then in a month or half a year they will not only yell, but they will beat," he said.
"I do not have the slightest doubt about it."
The authorities are struggling to know how to deal with the new tactics, which occupy a grey area between legitimate protest and violent intimidation.
A few days after Sroda's lecture was ambushed, around 20 young men tried to interrupt a lecture by Adam Michnik, the editor-in-chief of Gazeta Wyborcza, a leading liberal newspaper.
Internet footage shows them jostling with university security staff in Radom, about 100 km (60 miles) south of Warsaw, and shouting the same slogan, "Hit the red trash!". It was extra ironic; Michnik was one of Poland's most prominent dissidents in communist times.
In March, Robert Biedron, Poland's first openly gay member of parliament, was at a conference with other leftist politicians when around 30 young men in sports clothing gathered outside the hotel in Sandomierz, 220 km south of Warsaw.
"This is Poland not Brussels, here we do not support deviations!" they shouted in video footage on the Internet.
Some of the young men got past security personnel into the meeting hall while police stood by. Once in they shouted the "Hit the red trash...." slogan and "Get the fuck out of here!".
Biedron, a member of the liberal Palikot party, said he had heard of other such incidents involving far-right groups. "It fills me with horror to watch this," he said in an interview.
"These movements raise their heads today and, with increasing audacity, interrupt meetings and demand debates be canceled," Biedron said. "This is very dangerous and the authorities and the police are just passively watching."
Police spokesman Grzegorz Dudek said an oversight body would look into whether police at the hotel could have done more.
Sandomierz prosecutor Malgorzata Sowinska-Lalek told Reuters preliminary police findings indicated the group was made up mainly of fans of a local soccer club. She said her office would determine whether to press criminal charges of unlawful threats.
The anti-racist Never Again Association said it documented a 30 percent rise in the number of racist or xenophobic incidents and crimes linked to the far-right last year.
Analysts say economic slowdown plays a role. Youth unemployment is at a six year high of 29 percent as Poland's economy, which defied the euro zone crisis for years, grinds almost to a halt.
The far-right "flash mobs" have channeled unformed youthful aggression into disciplined operations with a political agenda.
The main far-right organizations deny organizing them but there is a trail of connections - from links on each other's Facebook pages to statements praising each other's activities - that tie the groups indirectly to the new tactics.
A group calling itself the Independent Academic Faction (NSA) has taken responsibility for the incident in Warsaw, saying it was staged to protest against the cancelling of a nationalist debate at the university.
Little is known about NSA, but it is affiliated with Ruch Narodowy, the informal umbrella movement for far-right groups that was launched in November last year at a nationalist demonstration after which some marchers clashed with police.
That movement is led by two main groups: Pan-Polish Youth and the National Radical Camp, which shares its name with an anti-Semitic party that was outlawed before World War Two.
Przemyslaw Holocher, a National Radical Camp leader, said his group was growing, but did not organize the "flash mobs".
"We do not dissociate ourselves from such initiatives, because they are grassroots social initiatives, which are an effect of leftists' ideologies throwing themselves around for many years," he said.
Robert Winnicki, who was leader of Pan-Polish Youth at the time of the Warsaw incident, denied organizing it, calling it an "eruption of students' discontent" at the cancellation of the nationalist debate.
"This was a happening, not well prepared, but a happening," he said, rejecting violence and using a term that usually describes an artistic performance.
"If it is a happening then I support it," he said.
Editing by Christian Lowe and Philippa Fletcher