Two RAF fighter jets were scrambled to intercept Russian military aircraft flying over the North Sea.
The Typhoons were launched from RAF Lossiemouth in Scotland after two Russian Tu-142 Bear F planes were detected near UK airspace on Saturday morning.
The RAF said the Russian aircraft are used for anti-submarine warfare and maritime patrol - and it is "essential" their movements are "carefully monitored" when operating so close to the UK.
Russian military aircraft flying within "the UK Flight Information Region" can be a "hazard" in the busy airspace over the North Sea, the RAF added in a statement.
It said such aircraft do not "squawk" by transmitting information on their position and movements to UK air traffic controllers, causing civilian planes to be re-routed to prevent them flying too close.
The Typhoons "shadowed" the Russian planes on Saturday to "deter this unprofessional activity and mitigate risks associated with Russian military aircraft flying in this busy international airspace", the RAF said.
An RAF Voyager aircraft from RAF Brize Norton in Oxfordshire was also deployed to provide air-to-air refuelling for the Typhoons, while Nato allies assisted with monitoring the Russian planes through the launch of "Quick Reaction Alert assets".
Controllers from RAF Scampton in Lincolnshire coordinated the mission, liaising with Nato partners at the Combined Air Operations Centre in Uedem, Germany.
An RAF spokesperson said: "The QRA crew did a fantastic job, locating aircraft that were not easy to detect very quickly.
"Again, the RAF has scrambled to defend the interests of the UK and Nato. It demonstrates the efficiency and resilience of our personnel, aircraft and systems."
The incident concluded by early afternoon, the RAF said.
