Russia has admitted for the first time that it suffered heavy casualties in an ill-fated operation against US-backed forces in Syria earlier this month.
The Foreign Ministry said "several dozen" Russians were injured and an unspecified number died in US airstrikes during the clashes on the night of February 7. The Kremlin had previously played down reports of mass casualties, saying only that five people may have died.
Moscow insisted the casualties were not Russian troops, saying "servicemen of the Russian Federation did not participate in any way" in the clash. It did not say what the Russians were doing there, but families of the victims say they were military contractors working for a Russian company, Wagner.
The casualties were sustained when a force numbering several hundreds, largely made up of the Russian contractors and a Christian militia loyal to the Syrian regime, advanced on an oil field held by US-backed militias who have been fighting ISIS in Syria.
According to accounts relayed to family members, the forces did not seem prepared for the ferocity of the response.
The Kremlin, which prefers to portray its intervention in Syria as largely an air war with few ground troops, had previously tried to downplay the story.
In its statement on Tuesday, the Foreign Ministry acknowledged that "several dozen" injured Russians were brought back to Russia where they were undergoing treatment at various medical facilities. Russians and other citizens of former Soviet Union countries were also killed in the attack, the ministry added, without providing numbers.
It insisted the contractors were working independently. "There are Russian citizens present in Syria who went there on their own," the statement said.
What happened during the clashes?
Moscow has provided no details of what the mercenaries were doing, but accounts of the operation have emerged in interviews with family members. The force crossed the Euphrates river near Deir Ezzor, a Syrian city held by ISIS until the end of last year, and advanced on the oil field controlled by the Syrian Democratic Forces (SDF).
But when the pro-regime forces began shelling an SDF base, the US responded with heavy airstrikes and artillery fire that lasted for about three hours.
US commanders tried to warn their Russian counterparts through protocols known as deconfliction channels. But the counterattack was underway by the time communications were established.
US defense secretary James Mattis has appeared to cast doubt on Russian claims that it had nothing to do with the contractors working on the ground.
"I doubt that 257 people all just decided on their individual own selves to suddenly cross the river into enemy territory and start shelling a location and maneuvering tanks against it," Mattis told reporters on a flight back to Washington from Europe at the weekend.
But Mattis said the US did not know who had given the orders. "Was it local direction? Was it from external sources? Don't ask me. I don't know," he said, according to a Pentagon transcript.
Families of the dead men have demanded an explanation for what happened. Farkhanur Gavrilova, 67, from the central Russian village of Kedrovoye, said she only learned of her son's death from an acquaintance.
She contrasted the fate of the Wagner men with state media coverage of Roman Filipov, the pilot shot down by rebels in Syria last month. "Are they not people too? They obviously went to fight, to help, even if it's for the money it's because of poverty, because there are no jobs," Gavrilova told Current Time, a Russian-language TV network run by Radio Free Europe/Radio Liberty.