MOSCOW -- In a case that has drawn renewed attention to ethnic tensions in Russia, a Moscow judge on Tuesday convicted a world champion mixed martial arts fighter, Rasul Mirzayev, of negligently causing the death of a Russian college student during a fight outside a nightclub here in August 2011.
Mr. Mirzayev, 26, was born in Dagestan and is one of tens of thousands of immigrants from the North Caucasus who live in Moscow. He was convicted of killing Ivan Agafonov, a 19-year-old Russian student.
After announcing the verdict, Judge Andrey Fedin ordered Mr. Mirzayev released based on time served. The maximum sentence was two years in prison and he had been jailed since shortly after the episode. Family members of the victim said that the sentence was insufficient and their lawyers pledged to appeal. Mr. Agafonov's father stormed out of the courtroom as the verdict was being read.
Dozens of ethnic Russian nationalists demonstrated outside the courthouse where the police, fearing violence, had formed a cordon. Several of the demonstrators were arrested including Dmitry Dyumushkn, a burly nationalist leader who once headed a group called Slavonic Union that has been banned in Russia as extremist.
Mr. Mirzayev, a featherweight fighter who stands 5 feet 7 inches and weighs about 145 pounds, admitted punching Mr. Agafonov in the face after an exchange of words that is alleged to have included an insult concerning Mr. Mirzayev's girlfriend. Mr. Agafonov fell, hit his head on a metal drain cover and died several days later.
Medical experts determined that there were some errors in Mr. Agafonov's care, and Judge Fedin noted that those mistakes also could have contributed to his death.
The dispute unfolded outside a nightclub, called Garage, where Mr. Agafonov had been drinking. He was apparently playing with a remote-controlled toy car and exchanged some words with a young woman who had accompanied Mr. Mirzayev to the club.
Grainy footage of the episode, captured by a nearby security camera, seemed to show a brief altercation, with Mr. Agafonov crumpling to the ground after a receiving a swift blow.
Mr. Mirzayev originally faced a more serious charge punishable by up to 15 years in prison, but prosecutors requested that it be reduced. The trial was delayed repeatedly by disputes over the testimony of medical experts and other procedural wrangling.
The case had echoes of an episode in 2010, in which an immigrant from the North Caucasus shot and killed a soccer fan in Moscow, setting off riots in a square adjacent to the Kremlin.
Mixed martial arts, in which fighters use both striking and wrestling techniques, traces its origins to the ancient Olympic sport of pankration, in which competitors were allowed to fight using all powers and were barred by the rules only from biting an opponent or gouging out the opponent's eyes. Mr. Mirzayev's future in the sport is uncertain.
This article originally appeared in The New York Times.