A Russian fighter aircraft made an "unsafe close range intercept" with a US Navy jet over the Black Sea today.

Pentagon spokesman Navy Captain Jeff Davis said in an emailed statement that the Russian Su-27 spent 19 minutes intercepting the US P-8A Poseidon and that the P-8 was conducting "routine operations in international airspace".

"US Navy aircraft and ships routinely interact with Russian units in the area and most interactions are safe and professional," Davis said.

"However, we have concerns when there is an unsafe manoeuvre like this. These actions have the potential to unnecessarily escalate tensions, and could result in a miscalculation or accident."

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AP reported the jet flew within 10 feet (3m).

Russian Defence Ministry Spokesman Major General Igor Konashenkov said that the Poseidon aircraft did not have its transponders turned on, and that it approached Russia's southern border twice.

He said Russian jets were deployed to intercept the incoming aircraft and "Russian pilots acted in strict compliance with international flight rules".

A senior US defence official said the Navy Poseidon had its transponder turned on during the entire flight.

The incident is just one in a series of interactions this year between Russian and US forces that are reminiscent of the Cold War, when unsafe flybys and aerial shows of force were a common occurrence.

In April, there were encounters over the Baltic Sea involving Russian aircraft buzzing the USS Donald Cook and an RC-135 reconnaissance aircraft in two separate incidents.

The Cook encountered a flight of two Russian swing-wing Su-24 bombers that came within 9m of the destroyer's rear deck and the US aircraft was on a "routine" mission when a Su-27 barrel rolled over it from wing tip to wing tip.

- additional reporting AP