Russian military jets attacked a remote base near the Jordanian border used by US and British special forces, the Wall Street Journal reported Friday citing military and intelligence sources.
The incident occurred a month ago at the base in south-eastern Syria, only 24 hours after a British special forces group had left the location, according to the article.
Following the airstrike, US central command in Qatar contacted the Russian headquarters in Latakia, Syria, and informed them the base was part of the US-led fight against Islamic State.
Ninety minutes after that warning, a second wave of Russian jets attacked the position, the paper writes.
Four rebels were reportedly killed in the airstrikes.
Washington has not offered an official reaction to the bombing incident. The Pentagon has confirmed there was an attack on June 16 near al-Tanf upon rebels that the US supports.
At a briefing held Friday, Christopher Garver, spokesman for Operation Inherent Resolve, declined to confirm the story.