A man who says he posted a video on the internet which appears to show the murder of two men, has surrendered to Russian police, reports say.
The two men are shown with their arms and legs tied
The man was being questioned in the town of Maikop, in southern Russia, officials told Russian media.
The video apparently shows two men being killed, execution-style, by far-right extremists.
A group calling itself the National Socialists of Rus says it carried out the attack.
Russian police are investigating the authenticity of the video.
Attacks on foreigners
The suspect is reportedly a young man who is a follower of far right-wing ideas.
He is not suspected of producing the material but of distributing it over the internet, a Russian interior ministry official was quoted by Interfax news agency as saying.
The clip, which was posted on some websites, shows one man apparently being beheaded and the other shot.
One was from Russia's southern republic of Dagestan and the other from Tajikistan, captions on the video say.
Violence against people from the Caucasus and from central Asian and other foreign countries has been increasing in Russia in recent years.
Russian interior ministry spokeswoman Irina Zubareva told RIA Novosti news agency that the video was posted on websites hosted by servers in foreign countries.
Relevant information had already been sent to the authorities in those countries, she added.
The video, which has been removed from some of the websites which earlier hosted it, shows the alleged killings to a soundtrack of heavy metal music.
The two men have had their arms and legs bound, and can reportedly be heard to say: "We were arrested by Russian national socialists."
Two men wearing masks and camouflage gear are shown giving Nazi salutes before the apparent killings go ahead.
Alexander Verkhovsky, an activist involved in monitoring racist crimes in Russia, told AP news agency that he had never heard of the organisation said to have carried out the attack, but the film appeared to him to be genuine.