Brussels: British foreign secretary Boris Johnson is describing Russian claims that it is not responsible for the poisoning of a former spy as absurd, and says the UK has the full backing of its European partners.

Johnson told reporters in Brussels Monday that “Russian denials grow increasingly absurd," with contradictory claims about whether Russia produced the nerve agent Novichok used in the 4 March attack that left Sergei Skripal and his daughter in critical condition.

He 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."

Johnson, speaking before briefing European Union (EU) foreign ministers on developments, said many in the bloc have been victims of “malign Russian behaviour" and that Moscow is “not fooling anybody anymore."