By Andrew Osborn and Maria Tsvetkova
MOSCOW (Reuters) - Britain accused Moscow on Wednesday of running an assassination programme to eliminate its enemies, while Russia said Britain may itself have orchestrated the poisoning of former Russian double agent Sergei Skripal and his daughter Yulia in England.
In remarkable scenes at a Russian Foreign Ministry event in Moscow attended by dozens of foreign diplomats and broadcast on state TV, the two sides launched sharp allegations against each other over the nerve agent attack.
The attack in Salisbury, England, has plunged ties between London and Moscow into their worst crisis since the Cold War. Britain has blamed Russia for the attack - something Moscow denies - and both have expelled diplomats in the standoff.
Russia had organised Wednesday's event to explain its stance and lost little time in alleging that Britain itself had either directly or indirectly orchestrated the attack or had allowed "a terrorist attack" to take place on British soil.
"Nobody understands what happened in Salisbury," Vladimir Yermakov, a diplomat who chaired the event, told foreign diplomats. "Let's investigate what really happened."
His own view, he said, was that the poisoning had been a pre-planned action designed to harm Russia.
Emma Nottingham, a British diplomat, countered that London had concluded it was "highly likely" that Moscow stood behind the attempted assassination of the Skripals for four reasons:
"The identification of the chemical agent by our world leading scientists, our knowledge that Russia has previously produced this agent ... Russia's record in conducting state-sponsored assassinations ... and our assessment that Russia views defectors as legitimate targets."
Many ambassadors including those of Britain, France, Germany and the United States, stayed away from the Moscow event, sending more junior officials instead.
Key Western countries criticised Russia and offered Britain their support.
"US & UK were right not to send our Ambassadors to @mfa_russia briefing to hear wild accusations and implausible denials. #Russia was responsible for the nerve agent attack," U.S. State Department spokeswoman Heather Nauert said on Twitter.
U.S. President Donald Trump and French President Emmanuel Macron reiterated solidarity with Britain in a telephone call on Wednesday and "agreed on the need to take action to hold Russia accountable", the White House said.
Some others, including Sweden and the Czech Republic, publicly complained about Russian accusations that their countries might have been the origin of the nerve agent used in the Salisbury attack.
Skripal, a former colonel in Russian GRU military intelligence who betrayed dozens of Russian agents to British intelligence, and his daughter Yulia have been critically ill since March 4, when they were found unconscious on a public bench in the English cathedral city.
Skripal took refuge in England after being released by Moscow in a spy swap deal involving the exchange of some Russian spies held in the West.
Britain says a military-grade nerve agent called Novichok, first developed by the Soviet Union, had been used in the attack.
But Nottingham said Russia had failed to explain how the nerve agent used in the attack had got from Russia to England and why it was running an illegal chemical weapons programme.
"Instead, what we've seen is a barrage of distortion and disinformation ... and attempts to confuse the facts."
Yermakov said Russia did not understand what was going in British officials' heads. Talk of the Novichok nerve agent was like something out of a British TV series, he said.
"Aren't you ashamed of yourself ?," Yermakov asked Nottingham. "Pull yourselves away a little bit from your Russophobia and your island mentality."
He said Moscow had nothing to do with the tragedy and wanted a wider investigation which, he said, meant London should share information and cooperate with Moscow.
Speaking on a visit to Japan, Russian Foreign Minister Sergei Lavrov said Russia wanted Britain to tell it where the Skripals were currently located.
Lavrov said Moscow also wanted to know why the British government had accused Russia of responsibility when the police investigation into the Salisbury incident was incomplete.
"Overall there is no doubt that the current British leadership has consciously taken a course to undermine Russian-British relations," Lavrov said at a news conference with his Japanese counterpart Taro Kono in Tokyo, according to a transcript on the Russian foreign ministry website.
"If this will continue in the form of any tangible new anti-Russian actions then of course nobody has cancelled the principle of reciprocity. It would be good for everyone and for (the British government) if they stopped getting agitated and calmed down."
(Additional reporting by Denis Pinchuk in Moscow and Doina Chiacu in Washington editing by Richard Balmforth)