MOSCOW — Three human rights groups announced on Monday a legal action that they say is the first to target soldiers from the Russian mercenary organization Wagner for crimes committed in Syria, highlighting growing efforts to hold accountable contract soldiers in war zones.
The case arose from the swirl of violence in Syria as multiple factions, contract soldiers and proxy forces fought one another outside the Geneva Conventions or other treaties on the laws of war. The legal filing tries to use a patchwork of national legislation and treaties to plug that hole, what the rights groups called an impunity gap for mercenaries even as they proliferate on modern battlefields.
“We are seeing a resurgence of mercenaries in armed conflicts around the world,” Ilya Nuzov, director for Eastern Europe and Central Asia at the International Federation for Human Rights, one of the groups that brought the legal action, said in a telephone interview. “Unfortunately, they commit grave human rights abuses.”
The case, if it ever comes to court, would seem easy to prosecute because those accused filmed themselves killing a man who they claimed was a member of the Islamic State militant group. It is not clear why they recorded the killing, but analysts said it might have been for propaganda reasons or as a horrific form of advertising.
In the video segments that have circulated online since 2017, a group of Russian-speaking men in the darkly theatrical, almost post-apocalyptic setting of the ruined Al Shaer gas plant in the city of Homs, in northern Syria, filmed themselves beating their victim with a sledgehammer, then dismembering and burning the body.
Rights organizations and analysts of the Syrian conflict have studied the clips for years. But the killing remained a crime without punishment because of the complicated jurisdictional issues related to contract soldiers.
Novaya Gazeta, an independent Russian newspaper, two years ago identified one of the attackers as a member of the Wagner mercenary group, which the United States government has said in sanctions documents is financed by Yevgeny V. Prigozhin, an oligarch who has been called “Putin’s chef” for winning catering contracts for the Kremlin.
The Kremlin has denied any ties to Wagner or to the Russian-speaking men who appear in the video.
Rights groups have compared the videotaped killing to shootings in Nisour Square in Baghdad in 2007 by security contractors with Blackwater, the American security company, an episode that became emblematic of the difficulties of prosecuting contractors. Four Blackwater guards were convicted in an American court but were pardoned last year by President Donald J. Trump.
Russian prosecutors have so far not opened an investigation. With their filing, the International Federation for Human Rights and two other organizations — the civil rights society Memorial and the Syrian Center for Media and Freedom of Expression — formally requested that they do so.
While the litigants concede it is unlikely that Russia will pursue an inquiry, they say that the filing is part of a legal strategy to move the case to the European Court of Human Rights, whose rulings Russia is bound by treaty to observe. To do so, they must first exhaust appeals in Russia’s domestic judicial system.
The case was filed on behalf of a brother of the man killed, who has been identified as Mohammad al-Abdullah. Rights groups say Mr. al-Abdullah defected from the Syrian Army but had no known connection to the Islamic State.
In the video of the killing, one of the Russian speakers says, “This will happen to every member of ISIS.” At least four of the people present filmed the episode on cellphones or with a small digital camera.
Aleksandr Cherkasov, chairman of Memorial, said the Russian authorities should prosecute the case to remove violent criminals from society and to uphold rules on the humane treatment of prisoners of war.
“Any cruelty to a captive will be answered by cruelty to Russian prisoners,” he said. “Any responsible officer in any army would be interested in this investigation.”
Mercenaries and other so-called nonstate combatants are a rising concern for human rights groups. About three-quarters of wars today are fought by such soldiers, rather than by members of nations’ armed forces, said Varvara Pakhomenko, a human rights consultant.
Western governments have accused Russia of deploying Wagner contract soldiers in the Central African Republic, Libya, Sudan, Syria and Ukraine.
In Syria, it was partly a moneymaking strategy. Under a program first revealed by Russian investigative reporters in 2017, the Syrian government granted companies with ties to the Russian security services mining, oil or natural gas rights in territories outside the Syrian state’s control. The practice was seen as an incentive for the companies to hire contract soldiers to capture the areas.