Britain's aircraft carrier in the Norwegian Sea was repeatedly approached by a Russian patrol aircraft before being escorted away by UK fighter jets, in the latest incident risking a potential escalation between NATO and Russia.
The incident, which Britain called "unsafe and unprofessional", comes before a NATO meeting in Ankara on Tuesday, where NATO members are set to pledge 70 billion euros ($A115 billion) in military assistance to Ukraine for 2026.
Britain said the Russian "Bear-F" maritime patrol aircraft passed at low altitude and "unnecessarily close" to HMS Prince of Wales, the aircraft carrier at the centre of a naval formation known as a carrier strike group, on July 2.
"The Bear-F ... dropped a large number of sonobuoys in close proximity to the carrier," the Ministry of Defence said on Monday, referring to devices which are used to detect and track submarines.
Two F-35 fighter jets from the HMS Prince of Wales were sent to intercept the Russian aircraft until it left the area.
Britain's carrier strike group is currently deployed under NATO's command in the High North, as part of efforts to boost North Atlantic security given concern over Russian aggression in the region.
Earlier in 2026, Britain deployed military vessels to prevent attacks on cables and pipelines by Russian submarines that spent more than a month in and around UK waters.
Britain said in a separate statement on Monday that defence minister Dan Jarvis had recently visited UK forces onboard the aircraft carrier in waters near Iceland.