Artist Pyotr Pavlensky lies on the ground, wrapped in barbed wire roll, during a protest action in St. Petersburg, Russia, on May 3. (© Stringer . / Reuters/REUTERS)

Artist Pyotr Pavlensky’s protest performances have begun to take on a familiar, if chilling, pattern. First, horrified policemen stare at him in confusion. Then they call a doctor.

On Friday, the 29-year-old’s audience swelled when the authorities announced they were investigating him for hooliganism, an increasingly frequent accusation here against anti-government demonstrators. Such charges turned into two-year prison sentences for three Pussy Riot punk-band singers and have kept 30 Greenpeace crew members, who had been protesting Arctic drilling, in jail since September.

The move against Pavlensky came after his latest protest, this past Sunday, when he traveled to Red Square from his home in St. Petersburg, sat down in front of Lenin’s tomb, stripped naked and nailed his scrotum to the paving stones.

“It was my appeal to society,” Pavlensky said Friday by telephone from St. Petersburg. “It’s not the authorities who hold people by their balls. It’s people themselves. The country will turn into a police state if people do nothing.”

He called the performance “Fixation.”

Pavlensky, a supporter of jailed members of female punk band "Pussy Riot", looks on with his mouth sewed up as he protests outside the Kazan Cathedral in St. Petersburg on July 23. (© Handout . / Reuters/REUTERS)

Yes, it hurt.

But overcoming fear and pain is part of the work.

“I tried to show that you can always act,” Pavlensky said. “I have the same fears and phobias as everyone else, but I was able to overcome them and act.”

In “Stitch,” his first performance, Pavlensky stood in front of St. Petersburg’s Kazan Cathedral in the summer of 2012 and sewed his mouth shut to protest the Pussy Riot trial. The young women had sung a song in Moscow’s main cathedral protesting the close relationship between church and government.

“The 10 holes around my mouth were minor wounds,” he said. Police called an ambulance, and doctors removed the stitches at the hospital. A psychiatrist examined him and declared him sane.

Pavlensky knew he had to act quickly Sunday at well-policed Red Square. He wore a long coat and loose pants. He turned his back to police, sat down and pulled off his pants.

“There are gaps between paving stones,” he said. “I drove the nail in there. I put my clothes and the hammer into my backpack and threw it away from me. Then the performance started. I was naked, sitting on Red Square, in front of Lenin’s tomb, looking at my testicles nailed to the stones. I was very quick. I think it took me a minute.”

Police approached immediately, he said. “The first phrase I heard was, ‘Sir, please stand up.’ ”

Pavlensky’s performances are intended to challenge the Russian power structure, not individual officers — but the officers inevitably become involved.

“No one had the courage to pull out the nail,” he said. “So they covered me up with a white blanket. Then they started to tell people to go away. Finally, they closed Red Square.”

The artist sat there for a half-hour or so until an ambulance arrived.

“The doctor was very confident,” he said. “The nail was very hard and strongly fastened. He very carefully pulled the nail from the stones. At the hospital they removed the nail, cleaned and bandaged the wound and gave me a tetanus shot.”

The next day, a city judge said she found no evidence that any law had been broken. Friday, Pavlensky got a call from Moscow saying he was under investigation — after he heard it on the news.

Pavlensky chose to protest Sunday because it was Russian Police Day, as well as the 75th anniversary of Kristallnacht, when Jews were attacked across Germany. “My idea was to tell people, ‘You will have Police Day the rest of your life if you don’t act,’ ” he said.

Last May, in a performance he called “Carcass,” he wrapped his nude body in barbed wire outside the St. Petersburg parliament building, protesting a host of repressive laws. Police had to wait for wire cutters. “The action turned into a very long performance,” the artist said. “They discussed for a long time what to do with me.”

Finally, the ambulance came.