Russia and Britain faced off on Wednesday trading accusations at a tense meeting of the world's chemical weapons watchdog, as Moscow accused British and US secret services of being behind the poisoning of a Russian former double agent.
London slammed as "perverse" a Russian proposal for a joint probe into the poisoning of ex-spy Sergei Skripal and his daughter Yulia with a nerve agent, dismissing it as a "diversionary tactic."
But Russian officials hit back that accusations of Moscow engineering the attack were a "grotesque provocation ... crudely concocted by the British and American security services."
British authorities say the Skripals were poisoned with the Soviet-designed nerve agent Novichok in the town of Salisbury on March 4, and said it was "highly likely" Moscow was behind it.
The crisis has sent the long-difficult relations between Russia and the West plummeting to new lows. Both sides have already expelled scores of diplomats.
Britain has also suspended high-level diplomatic contact with Moscow.
Russian foreign intelligence chief Sergei Naryshkin warned Wednesday in a speech in Moscow that both sides must avoid tensions escalating to the dangerous levels seen at the height of the Cold War.
At a closed-door meeting of the Organisation for the Prohibition of Chemical Weapons (OPCW) in The Hague, convened at the request of Moscow, Russia insisted it was ready to cooperate.
"We consider this is necessary to ensure that this problem is solved within the (international) legal framework," the Russian embassy to the Netherlands said in a Tweet.
It added that it had won backing from 14 other countries on the OPCW's governing executive council and its statement was "supported by solid facts by experts in this field."
But the British delegation to the OPCW said "Russia's proposal for a joint, UK/Russian investigation into the Salisbury incident is perverse. It is a diversionary tactic."
Moscow was seeking to "evade the questions the Russian authorities must answer," it added in a tweet."
The British defence laboratory analysing the nerve agent revealed Tuesday that it could not say whether the substance came from Russia. Moscow hailed that as a vindication of its repeated denials of involvement.