Norway says Russia has increased military flights in the Arctic
Four RAF F3 Tornado aircraft were scrambled in response to the Russian action, the UK's defence ministry said.
The Russian planes - long-range bombers - had earlier been followed by Norwegian F16 jets.
Russia recently revived a Cold War-era practice of flying bombers on long-range patrols.
In a statement the MoD said the eight Russian Tupolev Tu-95 Bear aircraft, flying in loose formation of four pairs, were initially intercepted by the Norwegian air force.
Radar tracking
They were tracked by the Norwegian aircraft until entering the Nato area for which the UK has responsibility in the early hours of Thursday morning.
Under established Nato procedures the MoD said it launched quick reaction alert aircraft in order to identify the bombers, as is routine.
Four F3 Tornados were launched in two waves from RAF Leeming, in North Yorkshire.
A Boeing E-3D airborne warning and control aircraft and a VC-10 refuelling tanker supported the operation, the MoD said.
The Russian bombers eventually altered course to leave the Nato zone, being tracked by UK aircraft and the radar station at RAF Boulmer, Northumberland.
Norway is following the increased Russian activity in the far north with interest
Lt Col John Inge Oegland
Norwegian armed forces
They were presumed to be heading back to their base.
The incident was the latest this summer in which British fighters have been used to warn off long-range Russian reconnaissance aircraft.
An MoD spokesman said: "The re-emergence of long-range flights from Russia is something the Russians are entitled to do.
"All countries have the right to maintain or up-grade and exercise their defence capabilities.
"The motivation behind any Russian military activity is a matter for the Russian government."
'Several incidents'
Earlier an MoD spokesman said the Russian bombers had approached but were not in British airspace.
Spokesman for the Norwegian armed forces, Lt Col John Inge Oegland, told the BBC the Russian bombers flew in international airspace from the Barents Sea to the Atlantic, before turning back.
Two Norwegian F-16s shadowed them on Thursday morning and another two went up later, he said.
There have been several similar incidents in recent months, Lt-Col Oegland added.
"Norway is following the increased Russian activity in the far north with interest," he told the BBC News website.
He said the Russian flights were not causing alarm in Norway. "Our systems are adequate," he said, when asked whether Norway was bolstering its security in the area.
F-16 fighter jet 
Four F3 Tornado fighter jets were launched by the United Kingdom's Royal Air Force to intercept Russian military planes. The eight Russian jets were flying in airspace patrolled by Nato, officials from the UK claimed. The long-range bombers were initially followed by Norwegian F16 jets, after Russia's recent decision to reinstate Cold War-style long-range patrols. 

14 strategic bombers were flying on long-range patrol, according to Russia's Defence Ministry. They also confirmed that none had approached a foreign state and had been shadowed by aircraft from Nato countries.  

The Ministry of Defence in the United Kingdom released a statement that the Russian Tupolev Tu-95 Bear aircraft, flying in four loosed pairs, were tracked by Norwegian aircraft before entering Nato airspace on Thursday morning. The UK currently holds responsibility for the Nato airspace, and launched four F3 Tornados from RAF Leeming in North Yorkshire, UK, to identify the bombers. The bombers eventually left the Nato zone, under tracking by UK aircraft and RAF radar in Northumberland. 

An MoD spokesman confirmed that Russia was entitled to its long-range patrols, adding 'The motivation behind any Russian military activity is a matter for the Russian government.' Lt Col John Inge Oegland, spokesman for the Norwegian armed forces, said there had been several similar incidents in recent months, but that the Russian flights were not causing alarm in Norway. 

Relations between Britain and Russia have worsened recently, particularly after Russia's refusal to allow the extradition of a former KGB bodyguard suspected of murdering emigre Alexander Litvinenko in London last year. Relations with Russia would "continue as normal outside the unresolved extradition request", a UK Foreign Office spokesman said.