A group of thugs in Russia's Siberian city of Irkutsk attacked members of a St Patrick's Day-themed flashmob after mistaking them for gay activists.
Interfax news agency reported a fight broke out after students from a language school held a belated St Patrick's Day celebration in a shopping centre in Irkutsk.
A spokesperson said: "On Sunday evening, members of Easy School held a St Patrick's Day flashmob in the mall. Some youths came up to them and expressed displeasure at the proceedings. A conflict took place that grew into a fight on the square outside the mall."
A law enforcement source said the fight was based on a misunderstanding over "non-traditional sexual orientation" - a Russian phrase meaning homosexual.
According to the source: "The Easy School members were wearing historic costumes, particularly kilts and their opponents mistook them for representatives of non-traditional sexual orientation."
The school posted a video of the flash mob on the social networking site VKontakte, which showed many wearing checked kilts.
The school confirmed both students and teachers were hurt in the fight. Police also confirmed a teacher at the school suffered mild concussion.
The school said in a statement: "Yes our students and teachers were among the injured but it could have been any young people who weren't to the taste of these grey masses."
Anti-gay violence has been rife in Russia since the announcement of the country's controversial anti-gay laws. Gay men and women were both targeted in the run-up to the Sochi Winter Olympics, as revealed by the Channel 4 Documentary Hunted.
In November 2013, a gay club in Moscow called Central Station was subject to a gas attack from an unknown assailant.
Last month, three men were found guilty of stabbing a man whom they suspected to be homosexual, before placing him in his car and setting the vehicle alight with petrol. The men were from a village in the eastern Russian region of Kamchatka.