MOSCOW - 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.