BRUSSELS (REUTERS) - British Prime Minister David Cameron warned the Kremlin on Friday that Russia would face far reaching consequences if it sent troops into Ukraine after a referendum in Crimea which he said has been carried out under the barrel of a Kalashnikov.

"Since we last met a sham and illegal referendum has taken place at the barrel of a Kalashnikov and Russia has sought to annex Crimea. This is a flagrant breach of international law and something we will not recognise," Cameron said.

"The best rebuke to Russia is a strong and successful Ukraine," Cameron said, adding that if Russian troops went into eastern Ukraine then the Kremlin would face "far-reaching consequences in a broad range of economic areas." When asked whether Roman Abramovich and other Russian tycoons should face sanctions, Cameron said: "We certainly haven't ruled anyone out from this approach." "You need to target people who have a direct relationship with the action that's been taken," he said.

Cameron said Russia is more dependent on Europe than Europe is on Russia.

"We should also remember that of course Europe is 25 percent or so reliant on Russian gas but if you look at Gazprom's revenues something like 50 percent of them come from Europe... So Russia needs Europe more than Europe needs Russia."