Vladimir Putin has rejected British accusations of Russian involvement in ex-spy Sergei Skripal's poisoning as "nonsense", adding that Moscow is ready to cooperate with London in the probe.
Speaking after winning a new term in a presidential election, Putin referred to the attack on Skripal and his daughter Yulia as a "tragedy", but added if the British claim that they were poisoned by the Soviet-designed nerve agent were true, the victims would have died instantly.
The 65-year-old said it was "nonsense" to think that anyone in Russia could have staged such an attack shortly before Sunday's presidential vote and before the World Cup that Russia is set to host this summer.
"As a whole, of course, I think any sensible person would understand that it would be rubbish, drivel, nonsense, for Russia to embark on such an escapade on the eve of a presidential election. It's just unthinkable."
In his first detailed comments about the poisoning, the Russian leader said Moscow was ready to cooperate with Britain in the investigation.
Putin's words come after Boris Johnson warned on Sunday that the UK is "in the Kremlin's crosshairs", effectively branding Moscow's EU ambassador a liar after Vladimir Chizhov claimed Russia had "nothing to do with" the Salisbury attack.
Amid deteriorating relations between the two countries, the Foreign Secretary dismissed Russian suggestions that the nerve agent could have come from a British military facility located 8 miles from the Wiltshire town as "satirical".
Johnson confirmed experts from the Organisation for the Prohibition of Chemical Weapons will come to the UK on Monday to test samples of the nerve agent used in the attack, but said he was convinced the poison was Russian-made Novichock.
He said Moscow has investigated ways of delivering nerve agents for assassination over the last 10 years in a breach of international rules.
Russia on Saturday expelled 23British diplomats and threatened possible "further retaliatory measures" after Theresa May last week kicked out 23 Russian diplomats who she claimed were undeclared intelligence officers.
Speaking on the BBC's Andrew Marr Show, Johnson was also grilled over his own party's links to Putin's regime, with the Foreign Secretary admitting he played tennis with the wife of former Russian minister who paid £160,000 at a fundraising auction for the game.
Johnson appeared on the show after Moscow's ambassador to the EU, Vladimir Chizhov, said his country was not involved in the poisoning of Russian double agent Sergei Skripal and his daughter Yulia.
Johnson said: "Listening to the Russian response, listening again to the response of the Russian ambassador to the EU with his satirical suggestion that this was done by UK agents from Porton Down, this is not a response of a country that really believes itself to be innocent.
"This is not the response of a country that really wants to engage in getting to the bottom of the matter."
When asked about Chizhov's claim that Russia stopped producing chemical weapons in 1992 and destroyed its reserves of such substances last year, Johnson said: "We actually have evidence, in the last ten years, that Russia has not only been investigating the delivery of nerve agents for the purposes of assassination, but it has also been creating and stockpiling Novichock."
Johnson said it was "obvious" that Vladimir Putin cared about the UK's attitude to Russia, adding: "That is one of the reasons why the UK is, as it were, in the Kremlin's crosshairs because they look at us and they think this is the country that time and again has called Russia out, has stood up to Russia when it comes to Crimea, when it comes to what they've been doing in Syria."
Appearing on the same show, Labour's Shadow Attorney General Shami Chakrabarti said she had yet to be convinced Putin was behind the attack.
She said: "It's either a loss of control, which by the way is pretty serious, including under the international chemical weapons convention and needs to be sorted if that is the issue, or it is what the Foreign Secretary is suggesting.
"But if he is suggesting that, that would be on the basis of new evidence that has not been shared with Jeremy Corbyn and it's not what Mrs May has said to date."
In an interview with the Mail on Sunday, Russian ambassador Alexander Yakovenko accused the Prime Minister of using the crisis to improve her image at the expense of relations with Moscow.
"In case of further unfriendly actions against Russia, the Russian side reserves the right to take further retaliatory measures – this is what the British Ambassador was told on Saturday," he said.
The Foreign Office confirmed scientists from The Hague will meet with officials from the Defence Science and Technology Laboratory and the police on Monday, and samples of the nerve agent will then be sent to international laboratories selected by the OPCW for testing, with results expected to take a minimum of two weeks.
Johnson will travel to Brussels to brief foreign ministers from across the European Union at a meeting on Monday on the attempted assassinations before holding talks Nato secretary general Jens Stoltenberg.
US media has reported Skripal may have been exposed to a deadly nerve agent through his car's ventilation system
The pair are still fighting for their lives after being exposed to Novichok in Salisbury two weeks ago.
ABC News is reporting that intelligence officials said the nature of the substance, described as "dusty", is now clear.
The US news outlet said UK officials now have a clearer picture of how the attack was carried out and that the Skripals may have been exposed to the substance through his BMW's ventilation system.
The development comes as counter-terrorism police renewed their appeal for sightings of Skripal's burgundy BMW 320D saloon car, registration HD09 WAO, in Salisbury on the morning of Sunday March 4.
Metropolitan Police Assistant Commissioner Neil Basu said: "We are learning more about Sergei and Yulia's movements but we need to be clearer around their exact movements on the morning of the incident."
Scotland Yard would not comment on the ABC News report.
ABC also reported that intelligence officials said that up to 38 individuals in Salisbury have been identified as having been affected by the nerve agent, but the full impact is still being assessed, and more victims sickened by the agent are expected to be identified.