Boris Johnson says it's 'overwhelmingly likely' Putin ordered nerve agent attack

British Foreign Secretary Boris Johnson says it's "overwhelmingly likely" Russian President Vladimir Putin ordered the use of a nerve agent against a former spy in the English city of Salisbury.

Prime Minister Theresa May has previously said it's "highly likely" the Kremlin is responsible for the attack on Sergei Skripal and his daughter Yulia.

But Johnson went a step further and blamed Putin directly on Friday. He said "our quarrel is with Putin's Kremlin, and with his decision, and we think it overwhelmingly likely that it was his decision to direct the use of a nerve agent on the streets of the U.K., on the streets of Europe, for the first time since the Second World War."

Putin's spokesperson Dmitry Peskov said in a statement carried by Russian news agencies that Johnson's statement was a "shocking and inexcusable breach of diplomatic propriety."

Russia to expel diplomats

Russia has also said it will expel British diplomats in a worsening global standoff over the nerve-agent attack on a former spy and his daughter, but still isn't saying when or how many.

Russian Foreign Minister Sergei Lavrov on Friday also accused Britain of violating international law, and said Britain's defence minister "lacks education."

The source of the nerve agent used — which Britain says is Soviet-made Novichok — is unclear. A report Friday in the Telegraph says it was put in the suitcase of Skripal's daughter before she left Russia for Britain to see her father.

Russia denies being the source of the nerve agent, suggesting it could have been another country, and has demanded Britain share samples collected by investigators. The mounting tensions come as Russians prepare to hand President Vladimir Putin a new term in an election Sunday.

Lavrov said Russia will "of course" expel British diplomats and that he hopes the Skripals recover soon so light can be shed on what happened.

Lavrov also lashed back at British Defence Secretary Gavin Williamson for saying Russia "should go away and shut up."

"Perhaps he also wants to go down in history with some loud statements.… I don't know, perhaps he lacks education," Lavrov told a news conference after talks on Syria's war with his Iranian and Turkish counterparts.

An 83-year-old whistleblower who helped develop Novichok said in an interview published Friday that he thinks the Skripals have little chance of surviving, and that only a few countries in the world have laboratories powerful enough to develop the nerve agent.

Vil Mirzayanov, who now lives in New Jersey, is quoted in Novaya Gazeta as saying the use of Novichok in Britain was a "shock."