Six people were injured Saturday, when a man threw an unknown substance at LGBT rights advocates in Moscow. The unnamed assailant attacked the group as they were leaving a conference on LGBT families.

It’s still not clear what was used in the attack, though initially it was believed to be some kind of acid. Mikhail Tumasov, director of Russian LGBT Network, said it smelled like acetone.

“I believe there was a person, a spy, who pretended to be an LGBTI person to get the correct information about the event which was hidden from the public,’ Tumasov told Gay Star News. He added that such attacks are not uncommon, forcing activists to come up with multiple backup plans.

"There should be no place for violence in the society," the board of Russian LGBT Network said about the most recent attack. "We express our support to the LGBT+ Moscow Resource Center and to the organizers of the Fourth Family LGBT+ Conference, and support the decision to postpone the event in order to ensure the safety of participants."

Some victims were knocked to the ground during the scuffle and suffered minor injuries. Police and ambulance were called to the scene but there a doubts any substantive investigation will take place.

"Some people filed the incident to the police," said Tumasov. "We will see if any action will be done to follow this hate crime."

While homosexuality is legal in Russia, anti-LGBT prejudice, both social and institutional, is rampant: A "gay propaganda" ban makes it a crime to promote "non-traditional sexual relationships" in public. Gay men have been trapped by extremist groups and brutally tortured on video. And in the former Soviet republic of Chechnya, dozens of suspected homosexuals have been detained by authorities as part of an orchestrated anti-LGBT purge.