"This use of a military-grade nerve agent, of a type developed by Russian Federation, constitutes the first offensive use of a nerve agent in Europe since the Second World War".
Putin spokesperson Dmitry Peskov was quoted by Russian news agencies as calling Johnson's statement a "shocking and inexcusable breach of diplomatic propriety".
Russian Federation is due to hold a presidential election on Sunday in which Vladimir Putin, himself a former KGB spy, is expected to coast to a fourth term in the Kremlin.
In a joint statement Thursday, President Trump, French President Emmanuel Macron, German Chancellor Angela Merkel and British Prime Minister Theresa May said they "abhor" the attack against Sergei Skripal, 66, and his 33-year-old daughter, Yulia, in Salisbury on March 4.
The Kremlin has vehemently denied it had a hand in the poisoning of its former spy in the English cathedral city of Salisbury early this month.
Unless the Russian government has backed down and responded privately, Britain is now expected to announce punitive actions targeting Russia on Wednesday.
Kremlin spokesman Dmitry Peskov said the United Kingdom was being "absolutely irresponsible".
"All the steps will be well thought out", Peskov said on Friday.
"We are anxious by this situation" and will work patiently to express Russia's position on the worldwide stage, Peskov said.
The spy, Sergei Skripal, had ceased to be an active threat to its interests. An autopsy showed he died from "compression to the neck", the police said in a statement, adding that there was no evidence he had been poisoned or to link his death to the attack on the Skripals.
What was the goal of this poisoning of a former Russian spy, apparently by the Russian state? "And we will not allow to be spoken to in that language either", he said.
He said Britain is making "wholesale accusations against Russia" before the inquiry into the spy poisoning is complete and "without proof".
In a statement to MPs Mrs May said that Russian Federation had provided "no explanation" as to how the nerve agent came to be used in the United Kingdom, describing Moscow's response as one of "sarcasm, contempt and defiance".
Johnson said the attack was a way for Putin to send a message to anyone considering taking a stand against it that "You do that, you are going to die".
Both father and daughter were found unconscious on a bench at a Salisbury beach, about 145 kilometers away from London.
He slammed people "distributing information that the programme allegedly existed", an apparent reference to Soviet chemist Vil Mirzayanov, who first revealed the existence of that class of ultra-powerful nerve agents.
"To create its components one needs powerful labs and very experienced personnel which only exist in several countries", the now US-based whistleblower told opposition newspaper Novaya Gazeta.
"As soon as we get the facts straight, if we agree with them, we will condemn Russian Federation or whoever it may be", President Donald Trump weighed in from Washington.
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