Russia is pushing its foreign policy in increasingly aggressive ways including cyber-attacks and espionage, posing a growing threat to Britain and the rest of Europe, the head of Britain's internal intelligence agency MI5 says.
As finance minister Philip Hammond unveiled the country's new five-year cyber security strategy and hinted at threats from Russia in a speech, the Kremlin dismissed the allegations as untrue and challenged its critics to produce evidence.
MI5 Director General Andrew Parker said Russia had been a covert threat for decades, but what differed now from the Cold War era was that there were more and more methods available for it to pursue its anti-Western agenda.
"Russia increasingly seems to define itself by opposition to the West and seems to act accordingly," he told The Guardian.
"It is using its whole range of state organs and powers to push its foreign policy abroad in increasingly aggressive ways, involving propaganda, espionage, subversion and cyber-attacks. Russia is at work across Europe and in the UK today."
Kremlin spokesman Dmitry Peskov told reporters that Mr Parker's words "do not correspond to reality".
"Until someone produces proof, we will consider those statements unfounded and groundless," he said.
Mr Hammond, at a technology conference in London, outlined Britain's strategy to boost its cyber security defences, part of a previously announced STG1.9 billion ($NZ13.6 billion) plan.
He said the government would strengthen its defences against attacks to protect its services and the economy, and would encourage industry to do the same to prevent cyber-attacks.
"So we will not only defend ourselves in cyberspace, we will strike back in kind when we are attacked," he said.
Already strained by the case of Alexander Litvinenko, a former KGB agent murdered in London in 2006, relations between Britain and Russia have further deteriorated over Moscow's actions in Ukraine and Syria.