Kremlin: 'UK must prove Russian involvement in poisoning or apologise'

"Sooner or later these unsubstantiated allegations will have to be answered for: either backed up with the appropriate evidence or apologised for," Vladimir Putin’s spokesman said on Monday right after the president had been elected to a fourth term.

The spokesman was also asked about whether the tensions with the West may have boosted Putin’s performance in the elections on Sunday.

"I wouldn’t use the phrase 'exacerbation of tensions with the West'. It's a question of this stream of slander, that is hard to explain and difficult to understand the motivation for, from the British side towards Russia," he said.

His comments came as experts from the Organisation for the Prohibition of Chemical Weapons (OPCW) were visiting the UK to analyse the nerve agent used against the former Russian spy and his daughter and were awaiting results.

Although the EU showed solidarity with the UK, asking Russia to explain how their nerve agent ended up in Salisbury, it didn’t flag the possibility of news sanctions being imposed on Russia and shied away for the time from pinning the blame on Moscow although it went as far as indicating that Russia was likely responsible.

UK Foreign Secretary, Boris Johnson on the other hand said, "What people can see is that this is a classic Russian strategy of trying to conceal the needle of truth in a haystack of lies and obfuscation."