A Russian Su-27 fighter jet intercepted and struck the propeller of a US military MQ-9 "Reaper" surveillance drone, causing it to crash into the Black Sea near the Crimean peninsula, the US military said.

Two Russian Su-27 jets carried out the intercept of the American spy drone, and one of them collided with it at 7.03am (6.03am Irish time yesterday).

Several times before the collision, the Russian fighter jets dumped fuel on the MQ-9 and flew in front of it in unsafe manoeuvres, the US military said in a statement.

"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," US Air Force General James Hecker, who oversees the US Air Force in the region, said in a statement.

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

Russia's defence ministry said that its fighter jets did not come into contact with the US drone, claiming instead that the drone crashed due to "sharp manoeuvring".

"The Russian fighters did not use their onboard weapons, did not come into contact with the UAV and returned safely to their home airfield," the defence ministry said.

A Russian SU-27 fighter jet (File pic)

The MQ-9 "Reaper" drone, which is built by General Atomics, has a wingspan of 20 metres and is about 11 metres long.

The drone weighs about 2,220kg when it is empty.

The Pentagon said it was forced to essentially crash the drone because of the damage caused in the incident.

Brigadier General Pat Ryder told reporters that Russia had not recovered the crashed drone at this point.

The White House said US President Joe Biden had been briefed about the incident.

White House spokesman John Kirby said that while there have been other such intercepts, this one was noteworthy because it was "unsafe and unprofessional" and caused the downing of a US aircraft.

"So it's unique in that regard," he said.

Mr Kirby said that the drone posed "no threat to anyone" and the US will continue to fly in international airspace over the Black Sea.

US summons Russian ambassador

The US has summoned Russia's ambassador to protest about the incident, the State Department said, while the US ambassador in Moscow has registered a "strong objection".

"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 US aircraft," spokesman Ned Price told reporters.

The US military said the incident followed a pattern of dangerous behaviour by Russian pilots operating near aircraft flown by the US and its allies, including over the Black Sea.

The Black Sea lies between Europe and Asia and is bordered by Russia and Ukraine among other countries.

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

A Western military source, speaking to AFP on condition of anonymity, said that diplomatic channels between Russia and the US could help limit any fall-out.

"To my mind, diplomatic channels will mitigate this," the source said.

Russia's invasion of Ukraine in February last year has led to heightened fears of a direct confrontation between Moscow and the Western NATO military alliance, which has been arming Kyiv to help it defend itself.

News of a missile strike in eastern Poland in November last year briefly caused alarm before Western military sources concluded that it was a Ukrainian air defence missile that had malfunctioned, not a Russian one.