Two Russian aircraft on Tuesday intercepted a US Air Force surveillance drone over the Black Sea, striking the drone’s propeller and forcing US forces to bring it down in international waters, according to US European Command, which caused the incident “unsafe and unprofessional”.

The collision occurred at around 8:03am Central European Time and involved Russian Su-27 fighter jets and an MQ-9 Reaper drone, the statement said. One of the Russian fighters struck the propeller of the drone, it said. “Several times before the collision, the Su-27s dumped fuel on and flew in front of the MQ-9 in a reckless, environmentally unsound and unprofessional manner,” the statement said. “This incident demonstrates a lack of competence in addition to being unsafe and unprofessional.”

There was no immediate reaction from Moscow, which has repeatedly voiced concern about US intelligence flights close to the Crimean Peninsula, which Russia illegally annexed from Ukraine in 2014. Since Russia’s invasion of Ukraine last February, which has heightened tensions between Moscow and Washington, the Russian Navy has controlled the Black Sea, effectively blockading access to Ukrainian vessels.

White House National Security spokesman John Kirby said US President Joe Biden was briefed on the incident by national security adviser Jake Sullivan. US Air Force General James B. Hecker, the commander of US Air Forces Europe and Air Forces Africa, said that the unmanned aircraft was “conducting routine operations in international airspace when it was intercepted and hit by a Russian aircraft.” The collision nearly caused both aircraft to crash, he said.