Two men inside a cage grapple on the floor, one violently pounding his opponent in a no-holds-barred sport banned in many countries while Russian crowds are going wild for more.
"Come on, hit him hard," screamed one of the thousand or so spectators jam-packed around the ring at a Moscow championship in mixed martial arts (MMA).
Often called "fight without rules" in Russian, the combat discipline was virtually unknown here a decade ago, but since then has become an officially recognised sport and gained thousands of fans.
New clubs are popping up all the time and not just for men. Women and children are also training in this extreme fighting style that allows almost any strikes or kicks, including from judo, boxing, taekwondo, karate, and kung fu.
Dating back to the 1920s, the discipline was popularised in the 1990s but did not catch on here until Russia's Fedor Emelianenko, a heavyweight fighter, won a series of international tournaments in 2001-2002.
"MMA is now very popular in Russia, almost as popular as boxing and other disciplines that have been around for much longer," said Ivan Ivanov, director of Rod, one of Moscow's major clubs.
When Rod opened its doors in 2007, it had only a dozen enthusiasts. Now, about 350 people train there, said Ivanov, a bearded former police officer with an imposing build.
"There are a lot of people from the security forces, but also many students and office workers," he said. The club admits children over the age of six, who can learn holding and striking techniques along with adults.
Biting, eye-gouging, and strikes to the throat or spine are some of the few techniques that are banned in the ring.
"It's the sport that most resembles a street fight," said Vyacheslav "Ali Baba" Yurovskikh, an MMA amateur who at 41 is one of the older competitors at Russian tournaments.
"It's cold in Russia, so we fight to keep warm," he joked, saying that despite his own broken nose and the sport's violent reputation, it is not that dangerous.
"In the ring there is a judge who will stop the fight in time," he said.
Sport mixed with nationalism and politics
A female fighter and Thai boxing champion, 22-year-old Anastasiya Yankova, got hooked the first time she tried MMA.
"In the ring, I have no fear. It's more like a rush of adrenaline. It's like a drug, a feeling that you want to repeat again and again," she told AFP.
Still, female fighting remains a rarity in Russia and some of the more fervent MMA participants are not happy with the idea.
The MMA subculture in Russia has also become mixed with nationalism as some clubs have strived to only train ethnically Slavic Russians rather than people from the mostly Muslim North Caucasus region, where combat sports are enormously popular.
Some amateur tournaments do not allow non-Slavic Russian fighters from the turbulent southern region, home to many of the country's successful wrestlers.
One major sponsor of MMA events is Russian clothing brand White Rex, which, according to the company's own advertising, aims to "recreate the fighting spirit" of the "white people of Europe".
And while the sport has drawn the attention of President Vladimir Putin, himself a black belt in judo, this has not thrilled some MMA circles who famously heckled him at one of Emelianenko's last fights, in Moscow in 2011.
Slavic nationalists are not natural Putin supporters and decry his policies to stabilise the North Caucasus with an injection of funding.
Putin was booed when he took the microphone in the huge Olimpiysky stadium to congratulate Emelianenko for defeating American Jeff Monson -- an incident explained away by Putin's spokesman Dmitry Peskov, who said the jeers were aimed at the fallen US contender.
But Anton Nemov, an MMA tournament organiser who was present, said the crowd was angry "basically because it was Putin." He added that many in the MMA community feel like the sport risks becoming more centralised and controlled now that it has been officially recognised.
Emelianenko, a Putin supporter and member of the pro-Kremlin United Russia party, last year traded his shorts for a suit and accepted Putin's invitation to join his council on sports and physical culture.
In October, Putin said he was "certain" martial arts would continue to grow in Russia, where 4.5 million people are already practitioners.