The Ministry of Defence released photographs of the latest in a series of incidents over the past few months in which the Russian planes flying close to British airspace have been intercepted by the RAF. The MoD said in a brief statement that the Typhoons, based at Coningsby in Lincolnshire and part of the RAF's quick reaction alert team, intercepted the Bear aircraft on Friday. Defence officials played down the incident describing it as a "picture-led story".

They made clear it was an opportunity to show off the air defence role of the Typhoon, an expensive and long-delayed aircraft originally designed in the cold war to engage in dogfights with Soviet planes over northern Europe. The Tupolev Bear was designed during the cold war as a long-range bomber.

First indications that Russia was flexing its muscles in this way came in May when Russian Bear aircraft flew towards British airspace during an exercise off Scotland, to spy on Royal Navy warships. Two Tornado F3 air defence aircraft were scrambled to see the bombers off.

On three occasions last month, as the row over Russia's refusal to extradite Andrei Lugovoy, suspected of murdering exiled dissident Alexander Litvinenko, caused tit-for-tat expulsions, Tornados were scrambled to warn off Russian Bear aircraft.

British intelligence officials are concerned that President Putin's ambitions are more serious than the mere rhetoric they initially hoped.

A defence official said Friday's interception was "appropriate" in the context of Nato guidelines.