Russian Prime Minister Vladimir Putin was greeted by catcalls when he stepped into the ring after a mixed martial arts fight at a Moscow arena on Sunday night.
The whistles and shouts, heard clearly on the live television broadcast, were an unprecedented rebuke as Putin prepares to return to the presidency next year.
A judo enthusiast, Putin has long been an admirer of Russian heavyweight mixed martial artist Fedor Emelianenko and came to see him take on American Jeff Monson.
After Emelianenko won, Putin stepped into the ring to congratulate him, but was met with catcalls from many of the 22,000 fans at the Olympic Stadium.
Russian Professional Boxing Federation spokesman Andrei Bazdrev said on Ekho Moskvy radio that Putin seemed taken aback by the unexpected negative reaction, but quickly regained his composure. Speaking over the din, Putin praised Emelianenko as a "real Russian bogatyr," a term for a medieval warrior.
The video was quickly posted on the Internet. "The end of an era," Alexei Navalny, one of Russia's best-known bloggers, wrote on Twitter.
While Putin remains highly popular in Russia, his approval ratings have fallen steadily in recent months. The independent Levada Center said polling done in late October showed Putin with 61 percent support, down from 77 percent a year ago.
Putin, who was president from 2000 to 2008, has announced plans to run for a third term in March. Even though he is all but certain to win the election, he has been actively campaigning for months, eager to show that he remains strong and vigorous at 59.
On Friday, he put on skates and invited television crews to film him playing a game with former hockey stars in which he was allowed to score.
Russians, however, are showing less tolerance for his televised publicity stunts, and this is particularly true in Moscow and other large cities where social media use is high.
Last month, Putin's spokesman was compelled to acknowledge that a diving expedition during which the prime minister had retrieved two ancient Greek jug fragments from the seabed was staged.