A Russian fighter jet collided with a U.S. surveillance drone in international airspace above the Black Sea, forcing the unmanned aircraft to crash, the U.S. said.

The Su-27 aircraft, accompanied by a second Russian jet, struck the propeller of the MQ-9 Reaper drone in what was an “unsafe and unprofessional” intercept at around 7 a.m. local time, U.S. European Command said. The two Russian fighter jets flew in front of and dumped fuel on the drone before the strike, it said.

“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,” Air Force Gen. James Hecker said. “In fact, this unsafe and unprofessional act by the Russians nearly caused both aircraft to crash.”

In February, the Pentagon scrambled fighter jets to counter four Russian aircraft that approached U.S. airspace. The U.S. military was on heightened alert following the shooting down of an alleged Chinese spy balloon and a series of other unidentified objects over U.S. airspace.