Russia could pose the "single greatest threat" to Britain, Foreign Secretary Philip Hammond warned in a speech Tuesday, while criticising "apologists" for Islamic State (IS) group militant "Jihadi John".
Hammond accused Russian President Vladmir Putin of "subverting" international rules which keep the peace between nations and said his actions in Crimea and eastern Ukraine "fundamentally undermine" the security of eastern European states.
Hammond said that Moscow's "aggressive behaviour" offered "a stark reminder that it has the potential to pose the single greatest threat to our security".
In a speech at British defence think-tank RUSI, the foreign minister sharply criticised those who he said sought to excuse the actions of "Jihadi John", the IS jihadist identified by media as Mohammed Emwazi, who grew up in London.
That was seen as a criticism of British civil rights group Cage, which worked with Emwazi for over two years before he went to Syria. "We are absolutely clear - the responsibility for acts of terror rests with those who commit them," Hammond said. "But a huge burden of responsibility also lies with those who act as apologists for them."
Cage has drawn sharp criticism in recent days for suggesting that the actions of British intelligence, who apparently tried to recruit him, helped radicalise Emwazi. In a rare speech focusing on the activities of the intelligence services, Hammond said that gathering intelligence on Russian capabilities would be a "vital part of our intelligence effort for the foreseeable future".
"We are now faced with a Russian leader bent not on joining the international rules-based system which keeps the peace between nations but on subverting it," Hammond said.
Moscow denies Western accusations that it backs the separatist militias fighting against government forces in eastern Ukraine.
However, journalists have repeatedly witnessed large deployments of military hardware coming from the direction of the Russian border, including advanced weapons that military analysts say could only have come from Russian arsenals.
Russian President Vladimir Putin has acknowledged ordering the annexation of Crimea from Ukraine last year in a move that sparked international condemnation.
In a sign of growing tensions, NATO forces are starting a major exercise in the Baltics. US officials say some 3,000 troops will take part in Operation Atlantic Reserve, which will last three months.
The exercise will see NATO forces working alongside their allies the former Soviet republics of Estonia, Latvia and Lithuania. Hammond also flagged the possibility of exposing the hidden, foreign financial holdings of Putin allies to the Russian public. "It's a very interesting thought," he said.