The head of the British Foreign Intelligence Service, Richard Moore, suspected Russia of conducting a stunningly reckless sabotage campaign in the West.
He stressed that his spies were working to keep the situation under control.
The head of MI6 said his agency and its French counterparts were working together to prevent a dangerous escalation, according to a Reuters article.
The two governments are assessing the risks in response to Moscow's statements.
A stunningly reckless campaign of Russian sabotage in Europe has been exposed, Moore said.
He explained that Russia is resorting to the nuclear saber-rattling claim to sow uncertainty about helping its allies.
“Such activity and rhetoric are dangerously irresponsible,” the MI6 chief stressed.
Western intelligence agencies suspect that Russian intelligence is trying to destabilize Ukraine's allies through sabotage, disinformation and arson.
Western officials have also linked Moscow to several attacks and arson attacks on cargo planes, a courier hub in Germany and a warehouse in England.
