BBC NewsRAF jets were scrambled on Wednesday after two Russian military aircraft were seen off the Cornwall coast, the Ministry of Defence has said.
The Russian Bear bombers did not enter sovereign airspace, it said.
On the same day, Defence Secretary Michael Fallon warned that Russia’s President Putin posed a “real and present danger” to three Baltic states.
Prime Minister David Cameron said the Russian action should not be dignified with “too much of a response”.
He added: “I think what this episode demonstrates is that we do have the fast jets, the pilots, the systems in place to protect the UK.
“I suspect the Russians were trying to make some sort of a point.”
BBC political correspondent Ross Hawkins said the appearance of Russian aircraft near the UK coast was a show of strength from the Russians, and such incidents were carried out with political intent because they would be reported on.
Our correspondent said it was part of a trend which had seen Russian aircraft flying close to UK airspace and there had also been concern about similar incidents in Europe.
It comes amid increased concerns over Russian involvement in the conflict in Ukraine and suggestions of Russian President Vladimir Putin’s potential future interference in Latvia, Lithuania and Estonia.
A ceasefire deal between government and pro-Russian rebel separatists in Ukraine was reached a week ago.
But battles around the strategic town of Debaltseve have seen the withdrawal of Ukrainian troops, while there was shelling in several places in eastern Ukraine, including the region’s biggest city, Donetsk, on Thursday.
‘New’ Cold War
Russia has denied helping the separatists, but it has been accused repeatedly of sending weapons and troops and using propaganda to inflame tensions.
And Russia’s UN ambassador Vitaly Churkin has labelled Ukraine’s call for the deployment of UN peacekeepers in eastern Ukraine as a destructive move.
Mr Cameron has said rebels in eastern Ukraine are using Russian military hardware, and that Mr Putin must understand there would be “economic and financial consequences for many years to come” if he did not change his behaviour.
Speaking to journalists from the Times and Daily Telegraph on Wednesday, Mr Fallon said the increase in Russian defence spending was “clearly worrying” and that he was also “worried about Putin”.
“They are modernising their conventional forces, they are modernising their nuclear forces and they are testing Nato, so we need to respond.”
Mr Fallon also said the prospect of a new Cold War was “warming up”.
“You have tanks and armour rolling across the Ukrainian border and you have an Estonian border guard who has been captured and not yet still returned.”
Previous incidents
He also said Russia was likely to use covert tactics such as those he said it had used to annex Crimea and during the current Ukraine conflict.
Mr Putin had also flown two other bombers “down the English Channel two weeks ago”, Mr Fallon added.
“We had to scramble jets very quickly to see them off.
“It’s the first time since the height of the Cold War, it’s the first time that’s happened.”
Russians, Russians everywhere! Look under your beds at night, look in your closets, no telling where Putin will popup next. He’s even flying obselescent prop planes in international airspace..the villain.