"On 17 September, Russia's airspace control means detected, above the neutral waters of the Black Sea, two aerial targets approaching the Russian state border. A Su-27 fighter jet was scrambled to identify the targets and prevent the border violation," the Russian Defence Ministry said in a statement.
The two planes were identified as the United Kingdom's reconnaissance Boeing RC-135 and the US Boeing P-8 Poseidon.
"The Russian fighter returned safely to the home airfield after escorting the foreign plane," the statement read on.
It was stressed that the flight of Su-27 was carried out in strict accordance with international rules for the use of airspace.