The head of Britain's foreign intelligence service has warned the Kremlin "not to underestimate" the West following a nerve-agent attack on a retired double agent in England that he attributed to covert Russian activity.
Alex Younger, head of the Secret Intelligence Service known as MI6, made the remarks on December 3 in a rare public speech, saying that Russia was in a state of "perpetual confrontation" with Britain and the West.
The speech comes at a time of heightened tensions between the West and Russia over issues including Moscow's aggression in Ukraine, its alleged election meddling in the United States and Europe, massive international cyberattacks, and the poisoning of Russian former spy Sergei Skripal and his daughter, Yulia, in the city of Salisbury in March.
The Skripals survived the poisoning, in which a Soviet-made military nerve agent known as Novichok was used.
Russia has repeatedly denied evidence that its agents were behind the attack and accused British intelligence agencies of staging the attack to stoke anti-Russian hysteria.
Two other British citizens were exposed to the nerve agent in June, apparently by accident; one of them, Dawn Sturgess, died.
Addressing students at the University of St. Andrews in Scotland, Younger said the Russian state "used a military-grade chemical weapon on U.K. soil."
"Our intention is for the Russian state to conclude that, whatever the benefits it thinks it is accruing from this activity, they are not worth the risk," he added.
Younger urged "Russia or any other state intent on subverting our way of life not to underestimate our determination and our capabilities, or those of our allies."
The expulsion of Russian diplomats from Britain and its allies following the Novichok poisoning in Salisbury had significantly reduced Russian intelligence capability, Younger said, emphasizing that "even as the Russian state seeks to destabilize us, we do not seek to destabilize Russia. We do not seek escalation."
The Russian Embassy in London rejected Younger's "unsubstantiated claims," which it said "sow a false atmosphere of fear and mistrust in British society," according to the Interfax news agency.
"It is only official London which is in constant confrontation with Russia, and at its own initiative," the embassy added.
In his speech, the MI6 chief also said that Britain's spies had thwarted multiple Islamic State (IS) plots originating overseas and that the country will fortify its intelligence ties with European counterparts even though the country is leaving the European Union next year.
In the most recent incident involving Britain and Russia, British Defense Secretary Gavin Williamson last week called on the public to report suspicious activity near army sites after a Russian TV crew prompted an alert at a highly sensitive military facility.
Williamson in October accused Russia of acting like a "pariah state," whose "reckless and indiscriminate" attacks had left it isolated in the international community.
And in an interview last month, the head of the British Army, General Mark Carleton-Smith, described Russia as a "far greater threat" to Britain's national security than Islamic terrorist groups such as the IS.