U.S. airstrikes in Syria killed 100 pro-regime forces including an unknown number of Russian contractors who were fighting alongside them. The conflict started when a force of around 300-500 soldiers armed with Russian made tanks and artillery came across the Euphrates River and began firing on a Syrian Democratic Forces (SDF) base. There were American advisers at the SDF base who called in an airstrike. From CNN:

Several Russians who had been hired as paramilitary contractors were among more than 100 men killed in US airstrikes in northern Syria last week, according to their friends and families.

The men were working for a private Russian company called Wagner, which has sent hundreds of private contractors to Syria to help both the Russian military and pro-regime forces, according to people who knew them.

One of the dead was 51-year-old Vladimir Loginov. Like many contractors who have gone to Syria, he was a member of a Cossack group of ultranationalists who have also fought in eastern Ukraine.

The exact number of Russians killed in the airstrike is unclear. Reuters reported yesterday that “dozens” had died, though that was unconfirmed. The New York Times also suggested dozens of Russians were killed in a report today:

Four Russian nationals, and perhaps dozens more, were killed in fighting between pro-government forces in eastern Syria and members of the United States-led coalition fighting the Islamic State, according to Russian and Syrian officials.

A Syrian military officer said that about 100 Syrian soldiers had been killed in the fighting on Feb. 7 and 8, but news about Russian casualties has dribbled out only slowly, through Russian news organizations and social media.

However, Bloomberg is reporting today that more than 200 Russian contractors died in the strike:

More than 200 contract soldiers, mostly Russians fighting on behalf of Syrian leader Bashar al-Assad, died in a failed attack on a base held by U.S. and mainly Kurdish forces in the oil-rich Deir Ezzor region, two of the Russians said. The U.S. official put the death toll at about 100, with 200 to 300 injured…

“This is a big scandal and a reason for an acute international crisis,” said Vladimir Frolov, a former Russian diplomat and lawmaker who’s now an independent political analyst. “But Russia will pretend nothing happened.”

Fox News adds that a Reaper drone also destroyed a Russian made T-72 battle tank on Saturday in the same area, three days after the airstrike that killed the Russian contractors. As for why deconfliction efforts between the U.S. and Russia didn’t prevent this, Voice of America reports the U.S. was in contact with Russia before, during and after the airstrike but the Russians had no control over the contractors:

U.S. military officials said the coalition was in contact with Russia before, during and after Wednesday’s attack and had alerted Russia to the presence of SDF forces in that area…

He called the attack a “perplexing situation,” adding that he could not give “any explanation for why” the pro-government forces would attack a well-established SDF headquarters…

When pressed on why the U.S. considered the communication a success when it did not prevent the pro-government force attack, Mattis told reporters on Thursday, “You can’t ask Russia to deconflict something they don’t control.”

“The fact that somebody chose to attack us, and the Russians are saying, ‘’It’s not us,’ and we are firing on them to stop the artillery fire, that, to me, is not a failure of the deconfliction line,” Mattis explained.

Putin has emphasized that no uniformed Russian soldiers were killed in the strike. Grigory Yavlinsky, a politician running for president in Russia, called on Putin to reveal exactly how many Russians were killed in Syria. “If there was large-scale loss of life of Russian citizens, the relevant officials, including the commander-in-chief of our armed forces (Putin), are obliged to tell the country about it and decide who carries responsibility for this,” he said.