A Russian fighter jet forced an American MQ-9 Reaper drone down after striking its propeller with the aircraft, U.S. military reported.

On Tuesday, the aircraft were flying over the Black Sea, which is considered international waters, when two Russian Su-27 fighter jets came up next to the Reaper. “One of the jets intentionally flew in front of and dumped fuel on the unmanned drone several times,” according to a statement from the U.S. European Command, per CNN.

After the propeller was damaged, the U.S. military was forced to bring the drone down over international waters.

“Our MQ-9 aircraft was conducting routine operations in international airspace when it was intercepted and hit by a Russian aircraft, resulting in a crash and complete loss of the MQ-9,” said Air Force Gen. James B. Hecker, commander of US Air Forces Europe and Air Forces Africa, in the statement, per CNN. “In fact, this unsafe and unprofessional act by the Russians nearly caused both aircraft to crash.”

How did Russia respond to forcing American drone down?

Russia denies causing the attack, saying the damage to the drone came from “uncontrolled flight” and that it was “a result of sharp maneuvering,” The Washington Post reported. The Russian Defense Ministry claims that when it was downed, the American aircraft was flying toward Russian borders with transponders turned off and classified the actions “as a violation of boundaries established by Moscow,” concerning the fighting taking place in Ukraine currently.

“The Russian fighters did not use airborne weapons, did not come into contact with the unmanned aerial vehicle and returned safely to their base airfield,” the statement said, per the Post.

What are Reaper drones used for in the U.S. military?

Air Force Brig. Gen. Pat Ryder said the U.S. military operates the Reaper drones in multiple regions to provide surveillance and it could possibly perform strikes. The drone in question “was conducting an intelligence, surveillance and reconnaissance mission,” Ryder told CBS News.

Ryder and other military personnel have not mentioned whether the drone was armed or not.

According to NBC News, the U.S. is sending Russian Ambassador Anatoly Antonov to the State Department for a meeting about the incident on Tuesday afternoon.