"'If you want to break up a demonstration, to toughen up your security forces at a rally, you can hire them,' said Kacper Rekawek, a researcher for the Counter-Extremism Project (CEP), a US-based charity.

'They've been used to target Russian liberals, the Russian opposition, Russian democrats, to simply beat them up. They are used to do the dirty job for others. They're not independent actors in that sense,' he added."