A U.S. aircraft shot down an unidentified drone deemed hostile toward coalition forces in At Tanf, Syria, a spokesman for Operation Inherent Resolve said Thursday.

The drone, similar in size to a U.S. MQ-1 Predator, was suspected to be "pro-regime" and was shot down Thursday by an F-15E Strike Eagle.

Army Col. Ryan Dillon said the drone was struck down after it was observed dropping a munition near coalition personnel training partner forces in the fight against the Islamic State.

Dillon, who replaces Air Force Col. John Dorrian as the operation spokesman, said the MQ-1-like drone "hit dirt."

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The drone released one of several munitions it was carrying -- and the action clearly wasn't "just a warning shot," Dillon said.

"It was clearly meant as an attack on coalition forces," he told reporters over video conference at the Pentagon. "They made very clear who they were trying to fire upon [but] were unsuccessful."

The drone "showed hostile intent, had munitions on it, and we shot it down," he said. The "pilot of that drone could be considered a threat as well."

Dillon didn't say where the drone came or took off from. There were no injuries to coalition advisers, but he didn't identify their nationality.

The drone strike marked the first time that forces supporting the Syrian government have attacked inside a so-called "deconfliction" zone near At Tanf, close to the Jordanian border, Dillon said.

The deconfliction zone is an area in which U.S. and Russian forces have agreed not to operate. The zone previously applied to airspace but now includes ground territory, a defense official told Military.com last month.

Dillon said U.S.-Russia deconfliction communications are open and in use. Russia, which supports the regime of Bashar al-Assad, reportedly made attempts to reach the pro-Assad forces on the ground last month during a similar strike. Dillon could not say whether messages relayed to the Russians got across regarding Thursday's incident.

"There is a deconfliction line," he said. "We have used that from the middle of May, when pro-regime forces first arrived."

The drone shootdown "follows an earlier engagement in the day in which coalition forces destroyed two pro-regime armed technical vehicles that advanced toward coalition forces at At Tanf inside the established de-confliction zone threatening coalition and partner forces," U.S. Central Command said in an email release following Dillon's video conference.

The strike against the pro-Syrian regime forces marks the third strike in recent weeks -- the second just this week -- by the coalition.

Defense Secretary Jim Mattis has said the pro-Syrian forces are backed by Iran, and have been knowingly operating "inside an established and agreed-upon deconfliction zone."

They are believed to be a threat to coalition forces in the region, he has said.

But CentCom stressed the coalition does not seek to fight Syrian regime forces, nor the Russian and pro-regime forces partnered with them.

"The demonstrated hostile intent and actions of pro-regime forces near coalition and partner forces in southern Syria, however, continue to concern us, and the coalition will take appropriate measures to protect our forces," the statement said.

Dillon added, "We are very well prepared and positioned to defend ourselves. We've clearly showed we are able to do that. We do not want to continue this everyday [as it] distracts from our goal to defeat ISIS."

-- Oriana Pawlyk can be reached at oriana.pawlyk@military.com. Follow her on Twitter at @Oriana0214.

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