Typhoon jets from RAF Coningsby - operating under Nato command - intercepted the two long-range Russian Bears and escorted them until they had left the “UK area of interest”, the Ministry of Defence said.
“At no time did the Russian military aircraft cross into UK sovereign airspace,” a spokesman said.
The latest incident, which occurred on Wednesday afternoon, came as Mr Fallon warned that tensions with Moscow appeared to be “warming up” in the wake of the international stand-off over Ukraine.
He said there was a “real and present danger” that Russian president Vladimir Putin could now repeat the tactics used to de-stabilise Ukraine against the Baltic states of Latvia, Lithuania and Estonia.
“Putin is as great a threat to Europe as Islamic State,” he told reporters travelling with him on a flight to Sierra Leone. “We’ve got to be ready for both.”
The latest incursion by Russian aircraft comes after a warship was intercepted by the Royal Navy close to UK waters and two long-range bombers flew down the English Channel off the coast near Bournemouth.
Mr Fallon said: “It is the first time since the height of the Cold War that has happened and it just shows you the need to respond each time he does something like that.”
The Defence Secretary expressed concern that the Russian leader could attempt a repeat of the covert campaign used in the Crimea and eastern Ukraine against the Baltic states.
That could involve irregular troops, cyber attacks and inflaming tensions with ethnic Russian minorities in nations seen as part of the country’s “near abroad” by Moscow.
“Nato has to be ready for any kind of aggression from Russia, whatever form it takes. Nato is getting ready,” he said.
“You have tanks and armour rolling across the Ukrainian border and you have an Estonian border guard being captured and not yet still returned.
“When you have jets being flown up the English Channel, when you have submarines in the North Sea, it looks to me like it’s warming up.”
His comments came after David Cameron said Europe could not turn a “blind eye” to the Kremlin’s actions and sanctions against Moscow could last “for many years to come”.
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