Washington DC - An unmanned US military drone collided with a Russian fighter jet in international airspace over the Black Sea in Eastern Europe, the US Air Force said.

The incident took place at about 2 AM EST Tuesday when two Russian Su-27 aircraft "conducted an unsafe and unprofessional intercept" of the MQ-9 surveillance drone, a statement by US Air Forces Europe said.

One of the two Russian jets struck a propeller on the drone, the statement 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," it continued.

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US forces brought 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 General James B Hecker, who is the 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," Hecker said in the statement.

Russia has not yet responded to the incident.

The US State Department has summoned the Russian ambassador to the US following the collision on Tuesday.

Anatoly Antonov reportedly arrived at the State Department in Washington.

"We are engaging directly with the Russians, again at senior levels, to convey our strong objections to this unsafe, unprofessional intercept, which caused the downing of the unmanned U.S. aircraft," said State Department spokesman Ned Price.

He called the move a "brazen violation of international law" but declined to say what response the US ambassador in Moscow received from Russia over the incident.