What exactly happened a week ago in the village of Khusham in eastern Syria? Have hundreds of Russian mercenaries been killed in an operation by the US military, as has been speculated for days in Russia? Or are such reports just a fake news campaign, which is how it has been represented by Moscow?

The answer to this question will determine whether the already strained relationship between the US and Russia will be put to the test again, with unpredictable consequences. The search for the truth is particularly difficult, because there are no reliable findings.

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Russia informed about US deployment

According to the US military, the picture is as follows: On the night of February 7 to 8, the Syrian Democratic Forces' (SDF) headquarters in eastern Syria's Khusham province of Deir el-Zor was attacked by forces loyal to Syrian President Bashar al-Assad. The SDF is an alliance which includes the YPG Kurdish militia, and it is supported by the anti-IS coalition led by the US. US military advisers were located at the SDF headquarters.

According to the Pentagon, when the attackers landed about 500 meters in front of the headquarters with heavy equipment including tanks, US forces reacted in "self-defense" with artillery and air strikes. More than 100 soldiers were killed.

It is alleged that the US had contact with Russian army representatives "before, during and after the operation," via a hotline. They provided assurances that there was no Russian army involvement in the attack on the SDF headquarters.

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Russian President Vladimir Putin meets Syrian President Bashar al-Assad in Sochi, Russia in November 2017

Victims belong to Russian 'Blackwater'

A few days after the incident, reports claiming high losses among Russian mercenaries in Syria appeared on Russian social networks and media. The number of deaths varies greatly. So far, various sources have confirmed the deaths of at least five Russians, while others claim that over 200 were killed.

There are recordings from alleged telephone conversations with Russians who survived the US attack. It is unclear whether these recordings are real, or who is behind them. The language and descriptions seem to be authentic and some details are consistent with other sources. According to these recordings, the motive behind the attack on the SDF headquarters in Khusham was to occupy an oil refinery.

Most victims on the Russian side are believed to be soldiers from a private military company. There is talk about a so-called "Wagner Group," named after its commander. According to Russian media reports, this is a mercenary troop of former Russian military personnel based on the US model "Blackwater" that has been operating illegally. There is no Russian legislation on private military companies.

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From the Urals via eastern Ukraine to Syria

In recent years, there have been several Russian media reports about the "Wagner group" fighting on the side of pro-Russian separatists in the conflict in eastern Ukraine. Apparently, a number of Russian fighters had moved from eastern Ukraine to Syria, including 38-year-old Stanislav Matveyev from the small town of Asbest in the Urals.

Only a few of the Russian mercenaries believed to have been killed in Syria have been named in media reports. In an interview for the news portal Znak, Stanislav Matveyev's widow, Elena, said that she had heard about her husband's death on February 9, 2018. She received a phone call from a local Cossack leader, who had been given the message by someone from eastern Ukraine.

She had tried to stop her husband from travelling to Syria, the woman said. Now she wants the Russian government to take revenge for the fallen mercenaries.

Debris from the Russian Su-25 fighter jet shot down over Idlib, Syria in early February

Officially, Moscow denies having any involvement in the incident in Khusham. Reports about hundreds of dead Russians are an example of "classic misinformation," according to an anonymous source from the Russian foreign ministry, who was quoted by the Moscow-based Interfax news agency on Wednesday.

"We in the Kremlin have no detailed information from which to draw conclusions," said Dmitry Peskov, spokesperson for President Vladimir Putin. "We cannot rule out the possibility that Russian citizens were on Syrian territory. But they are not part of the Russian armed forces."

Other recent Russian casualties

But the Russian armed forces, whose partial withdrawal from Syria was announced in December, have also suffered an increasing number of losses in recent times. A Russian Su-25 jet was shot down just days before the incident in Khusham. The pilot, however, died in battle on the ground. On New Year's Eve, two soldiers were killed when the Russian air base at Hmeimim was attacked.