UK Royal Air Force (RAF) Typhoon fighters have been scrambled to intercept four groups of Russian aircraft.
Two Typhoons from 3 (Fighter) Squadron were launched on 17 June following detection of the aircraft by Nato air defences in international airspace near to the Baltic States.
The aircraft were subsequently identified as a Russian Tupolev Tu22 Backfire bomber, four Sukhoi Su27 Flanker fighters, one Beriev A50 Mainstay early-warning aircraft, and an Antonov An26 Curl transport aircraft.
The UK Ministry of Defence said that the aircraft appeared to be carrying out a variety of routine training; the RAF Typhoons monitored the aircraft and escorted on their way.
An unnamed Nato official was quoted by Reuters as saying that the Russian aircraft were armed and were in the vicinity of Nato airspace.
The alliance intercepted the aircraft as they did not file a flight plan and did not use their transponders, which made them invisible to civilian air traffic control and a safety hazard to commercial air traffic, the official added.
Typhoon Detachment wing commander Ian Townsend said the detachment regularly intercept Russian and civilian aircraft from the UK Quick Reaction Alert (QRA).
The mission type is core business for the detachment and is exactly what it has been deployed for by Nato to perform in the Baltic region, Townsend added.
Britain has deployed four Typhoons to the Siauliai Air Base in Lithuania, last month, as a demonstration of support by Nato amid the political turmoil in Ukraine.
Last month, US fighter jets intercepted four long-range Russian Tu-95 Bear H bombers near Alaska, Northern California; the Russian aircraft flew within 50 miles of the northern California coast, but did not enter the US airspace.
Image: A Royal Air Force Typhoon fighter jet in flight. Photo: RAF/MOD Crown Copyright 2014.