The US military has claimed that a Russian fighter jet on Tuesday dumped fuel on an American drone over the Black Sea and then collided with it, causing the drone to crash.

US European Command said two Russian Su-27 fighters intercepted the unmanned MQ-9 Reaper over international waters and one clipped its propeller.

“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,” it said.

However, Moscow denied causing the crash of the drone, which the Pentagon said was on a routine intelligence, surveillance, reconnaissance mission.

“As a result of a sharp manoeuvre… the MQ-9 unmanned aerial vehicle entered an uncontrolled flight with loss of altitude and collided with the surface of the water. The two Russian jets had no contact with the US aircraft and did not use their weapons,” ,” the Russian Defence Ministry said.

The US State Department said it had summoned Russia’s ambassador to protest.

White House national security spokesman John Kirby later said, “obviously, we refute Russia’s “denial.” He said that the US was taking steps to recover and prevent the drone from being taken by someone else in an oblique reference to Russia.

“Without getting into too much detail, what I can say is that we’ve taken steps to protect our equities with respect to that particular drone — that particular aircraft,” Kirby told CNN.

“We obviously don’t want to see anybody getting their hands on it beyond us.”

Russian intercepts over the Black Sea are common, Kirby told journalists in Washington, but this one “is noteworthy because of how unsafe and unprofessional it was, indeed reckless that it was”.

NATO diplomats in Brussels confirmed the incident, but said they did not expect it to immediately escalate into a further confrontation, according to an AFP report.

The United States uses MQ-9 Reapers for both surveillance and strikes and has been operating them over the Black Sea with an eye on Russian naval forces.

“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 US Air Force General James Hecker, commander of US Air Forces Europe and Air Forces Africa.

“In fact, this unsafe and unprofessional act by the Russians nearly caused both aircraft to crash.

“US and allied aircraft will continue to operate in international airspace and we call on the Russians to conduct themselves professionally and safely,” he added.

Pentagon spokesman Brigadier General Pat Ryder told journalists the drone was “unflyable and uncontrollable so we brought it down.”

Several US Reapers have been lost in recent years, including to hostile fire.