RAF fighters were scrambled after two Russian bombers were spotted off the Cornish coast as Defence Secretary Michael Fallon warned the West must be ready to stand up to aggression from Moscow.

Typhoon jets from RAF Coningsby in Lincolnshire - 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 yesterday 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".

Ukip leader Nigel Farage however blamed the desire of Western governments to expand Nato and the European Union for triggering the latest instability.

"I've looked at what Michael Fallon said today. I have to say there's one missing part to everything that is being said and that is, actually, who was it that really started all this?" he said during a campaign visit in Kent.

"I'm not defending Putin's behaviour since, but we still aren't capable of actually admitting that it was us, through expansionism, through wanting Nato and the EU to expand to include the Ukraine, that actually began much of this instability."

Mr Farage insisted that he was "no supporter of Putin" and acknowledged that if Russia moved against Latvia, Lithuania or Estonia - which are all Nato members - the alliance would have to act.

"Let me be clear, if Putin were to act in an untoward manner in Latvia, Lithuania or Estonia, we are a Nato member so we would have to honour that. I really couldn't be clearer about that," he said.

For Labour, shadow foreign secretary Douglas Alexander said that the West needed to be ready to extend sanctions against the Kremlin if Mr Putin refused to change course.

"President Putin clearly has a strategy for the Baltic states - that emphasises dependence on natural gas and the manipulation of Russian minorities - which needs to be recognised and responded by both the EU and Nato," he said.

"President Putin risks further isolating Russia on the world stage if he continues to display belligerence and aggression in the face of established international laws and norms."

Nick Clegg said: "Vladimir Putin is rewriting the rules by which civilised nations conduct their affairs in Europe."

There is no evidence yet that Mr Putin is making an effort to destabilise the Baltic states, he suggested.

"Clearly, when the leader of a powerful nation like Russia starts throwing their weight around, there is a need to be vigilant. It is extremely worrying and it is essential that we stand together in the face of that sort of provocation."

Mr Cameron said that Moscow appeared to be trying to make "some sort of a point" with the latest incursion by Russian warplanes.

"I think what this episode demonstrates is that we do have the fast jets, the pilots, the systems in place to protect the United Kingdom," he said during an event at Felixstowe in Suffolk.

"I suspect what's happening here is that the Russians are trying to make some sort of a point and I don't think we should dignify it with too much of a response."