File photo. A US MQ-9 Reaper drone taxis in Nevada. Photo: AFP / Getty Images
A Russian fighter jet has collided with a US drone, causing the unmanned US aircraft to crash into the Black Sea, the American military says.
It says the drone was on a routine mission in international airspace when two Russian jets tried to intercept it.
The US European Command said Tuesday's crash was the result of an "unprofessional act by the Russians".
At a Pentagon briefing, US Air Force Gen Pat Ryder said the MQ-9 Reaper done was intercepted by two Russian SU-27 aircraft.
Ryder said the US drone was unmanned and was flying over the Black Sea when its propeller was struck.
He called the incident "reckless and unprofessional".
"Several times before the collision the SU-27s dumped fuel on and flew in front of the MQ-9," he said.
He added US forces routinely flew over international airspace to "bolster collective European defence and security" with allies.
"We call on the Russians to conduct themselves professionally."
Russia said the drone crashed after a "sharp manoeuvre", and denied that the two aircraft made contact.
The Russian defence ministry said the US aircraft was flying with its transponders turned off. Transponders are communications devices that allow the aircraft to be tracked.
The incident happened at about 7.03 Central European Time, according to the US military.
MQ-9 Reaper drones are surveillance aircraft with a 20m wingspan.
White House spokesman John Kirby said Russian intercepts of US aircraft were not uncommon over the Black Sea, but it was the first time that one had resulted in a crash.
Tensions have risen in the region ever since Russia's annexation of Crimea in 2014.
Since Russia's full-scale invasion of Ukraine the US and the UK have stepped up reconnaissance and surveillance flights, though always operating in international airspace
- BBC