The UK has accused Russia of carrying out an "unsafe close pass" of a Royal Air Force jet in international airspace.
A Ministry of Defence (MOD) spokesperson said the incident happened over the Norwegian and Barents seas on Monday during a routine operation.
Forces News has been told at no point did the RAF RC-135W Rivet Joint, an electronic surveillance aircraft, enter Russian airspace.
However, the state-owned Russian news agency TASS reported earlier that Russia's defence ministry said the RAF jet had entered Russian airspace.
Moscow's defence ministry claimed the aircraft was forced out of Russian territory by the crew of a Russian fighter jet, TASS also reported.
An MOD spokesperson denied this version of events, instead accusing the Russian aircraft of an "unsafe" maneouvre.
"A Russian MIG-31 jet conducted an unsafe close pass of an RAF RC-135W Rivet Joint aircraft as it carried out a routine operation in international airspace over the Norwegian and Barents Seas on Monday 15 August," the spokesperson said.
"The UK aircraft was in communication with Russian civilian air traffic control and its crew operated in a safe and professional manner."
The Rivet Joint aircraft later returned safely to its UK base.