Washington (United States) (AFP) - The outgoing head of the CIA appeared to confirm Thursday reports that around 200 Russian mercenaries were killed in February during a clash with US-led forces in Syria.

"In Syria, a handful of weeks ago, the Russians met their match and a couple hundred Russians were killed," Mike Pompeo said, during a Senate hearing on his nomination to become US secretary of state.

Pompeo did not go into more detail, but media reports have suggested that Russian mercenaries working for the so-called "Wagner Group" were involved in the February battle.

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Russia acknowledged at the time that five of its citizens had died when US-led coalition forces working alongside Kurdish militia called in air support to repulse an attack by Syrian regime forces.

Washington said the coalition had killed at least 100 "pro-regime" forces and a group of Russian investigative bloggers established the identity of dozens of named Russian fatalities.

Multiple reports have suggested Wagner operates a shadowy private army in Syria with the tacit assent of the Kremlin, which has also deployed Russian regulars to back Bashar al-Assad's regime.

President Donald Trump has nominated Pompeo to become Washington's top diplomat and his confirmation hearing came just as the White House mulls a strike to punish Assad for an alleged chemical attack.