Two fringe nationalist groups called the National Liberation Movement (NOD) and SERB harassed attendees and poured ammonia on an employee of the Canadian Embassy in Moscow, organizers said. The two groups are known for attacks on opposition activists and art exhibits .

Pro-Kremlin activists tried to shut down the opening of an LGBT film festival in Moscow on Thursday.

“People stood with posters depicting neo-Nazi and extremist symbols and acted aggressively,” the Side by Side festival organizers wrote on its Facebook page.

The organizers accused law enforcement of inaction and said that a senior officer attempted to put pressure on the venue to stop the festival. They later said that police took control of the security situation.

Photographs from the opening showed half a dozen people dressed in white medical coats waving the Soviet flag with NOD insignia. They were seen wearing tags that say “emergency psychiatric care.”

Police detained around 10 of the estimated 30 to 40 pro-Kremlin activists, the Dozhd TV news channel reported, citing a volunteer.

The Side by Side International LGBT Film Festival runs in St. Petersburg every year since 2008. Its offshoot in Moscow wraps up this Sunday.

According to a poll released earlier this week, an increasing number of Russians support equal rights for LGBT citizens.