A Russian fighter jet fired flares directly at an American MQ-9 Reaper drone over Syria on Sunday, damaging its propeller, according to U.S. Air Forces Central -- the latest in a string of what military officials have denounced as risky and provocative behavior.

The drone was on a counter-terrorism mission against the Islamic State group, according to the Air Force.

"On 23 July, 2023 at 12:23 a.m. (EST) Russian fighter aircraft flew dangerously close to a U.S. MQ-9 drone on a defeat-ISIS mission, harassing the MQ-9 and deploying flares from a position directly overhead, with only a few meters of separation between aircraft," Air Forces Central Commander Lt. Gen. Alex Grynkewich said.

One of the flares hit the drone, "severely damaging its propeller," according to Grynkewich.

"The Russian fighter's blatant disregard for flight safety detracts from our mission to ensure the enduring defeat of ISIS. We call upon the Russian forces in Syria to put an immediate end to this reckless, unprovoked, and unprofessional behavior," he said.

The crew remotely operating the MQ-9 was able to maintain control of the aircraft and fly it back to its home base.

The U.S. military has recently observed what it has called increasingly "unsafe and unprofessional" incidents in the sky.

Last week, a Russian Su-35 fighter endangered the crew of a manned U.S. MC-12 by forcing it to fly through its wake turbulence, according to a release from Air Forces Central.

"This reduced the crew's ability to safely operate the aircraft and put the four crewmembers' lives at risk," the release stated.

And for two days in a row early this month, officials have said, Russian pilots dropped parachute flares into the paths of U.S. MQ-9 Reaper drones, which took evasive maneuvers to avoid damage. Russia claimed the drones had entered airspace designated for a Russian-Syrian counter-drone exercise.

A senior U.S. defense official told reporters there was no such exercise, saying, "It's just an excuse to go after our MQ-9's and try to intercept."

Similar incidents have occurred outside Syria. In March, a Russian fighter collided with a U.S. drone over the Black Sea, bending its propeller. The U.S. was forced to bring the craft down off the coast of Ukraine, according to defense officials.

The U.S. has around 900 troops in eastern Syria assisting in the fight against IS, while Russia has a military presence in northwestern Syria as part of its mission to support Syrian President Bashar al-Assad.

Russian and U.S. forces for years have made use of a "deconfliction hotline" to let each other know when they are carrying out missions so as to avoid any dangerous misunderstandings.

The hotline is still used, but "it sometimes gets very heated," with a lot of back and forth during tense encounters, according to the senior U.S. defense official.