Russian President Vladimir Putin mockingly suggested on Tuesday that participants in unsanctioned protests were welcome to go to prison and “get shaved.”

In the latest in a series of interviews with state-run news agency TASS, Putin said opposition supporters who take part in unapproved rallies should expect to be given jail time.

“If you have not received (permission) and taken to the streets — you are welcome to get shaved,” Putin said, in reference to the practice of prisoners having their heads shaved.

“Get some rest. Relax a little bit,” Putin said. 

“There are certain rules for everybody to adhere to,” Putin told Andrei Vandenko, who is doing a series of interviews with Putin to mark 20 years since he first became president.

“This is the law. And it must be obeyed. Otherwise, the country’s stability will break down. Do we want to see cars torched in our streets?”

Police cracked down last summer on a series of unsanctioned anti-government demonstrations, with hundreds arrested and several protesters sentenced to long jail terms. 

Russia requires organizers of demonstrations to obtain prior approval from authorities and the opposition complains that permission is often denied without cause. 

Authorities imposed harsher penalties for organizing unsanctioned demonstrations after large-scale protests in 2011-2012 sparked by Putin’s return to the Kremlin after four years as prime minister.

Single-person pickets are the only form of protest that does not require prior approval from Russian authorities.

Putin has not shied away from using colorful or even foul language during his 20 years in power. In 2012 he used slang to refer to two-year jail sentences against three members of feminist punk band Pussy Riot and in 1999 famously vowed to “rub out (terrorists) in the outhouse.”