The West has been warned of a "world catastrophe" in a scathing verbal attack from former Russian president Dimitry Medvedev today following reports that Putin has ordered Russia's military to conduct a range of nuclear weapons tests.

In the address, Medvedev slated Western leaders as "infantile morons" and "irresponsible scoundrels" and claimed the deployment of Western troops in Ukraine - which he called a "non-existent country" - would merit a terrifying Russian response, from which no heads of state would be able to hide.

Medvedev said: "The chorus of irresponsible scoundrels among the Western political elite calling for troops to be sent to a non-existent country is growing.

"Now it includes representatives of the US Congress, French and British leadership, and individual madmen from the Baltic states and Poland.

"They also call for the active use of their missile weapons, which they supplied to the Banderites [a pejorative term for Ukrainians named after a hard-right faction of the Organisation of Ukrainian Nationalists], throughout Russia.

"And this is not a spring aggravation, but a cynical calculation for political dividends. There is some kind of total degradation of the ruling class in the West... This class really does not want to logically connect elementary things.

"Sending your troops to Ukrainian territory will entail the direct entry of their countries into the war, to which we will have to respond - and, alas, not in Ukrainian territory.

"In this case, none of them will be able to hide - either on Capitol Hill, or in the Elysee Palace, or in 10 Downing Street. A world catastrophe will come.

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"By the way, Kennedy and Khrushchev were able to understand this more than 60 years ago, but the current infantile morons who have seized power in the West do not want to understand.

"And that is why today the General Staff began preparations for the exercises, including activities for practical testing of the preparation and use of non-strategic nuclear weapons."

The address came as Nigel Casey, the British Ambassador to Russia, was summoned to the country's foreign ministry, according to Russian state media outlet Tass.

While Tass said the reason behind calling in Casey was unclear, it made a link between his summoning and a Reuters interview with British Foreign Secretary Lord Cameron in which he argued Ukraine had a right to use UK-provided weapons to strike targets inside Russia.

It also follows the news that Vladimir Putin has ordered Russian forces in the country's Southern Military District, including branches of the army, navy and air force, to engage in a set of tactical nuclear weapons drills.

While some Western and Ukrainian officials have said Russia is scaremongering via its nuclear weapons threats, the Kremlin has repeatedly indicated that it would consider breaking the nuclear taboo if Russia's existence was threatened.

Andriy Yusov, a spokesperson for Ukrainian military intelligence, said: "We do not see anything new here - nuclear blackmail is a constant practice of Putin's regime."

Kremlin spokesman Dmitry Peskov has called Western statements about sending Nato soldiers to Ukraine "a completely new round of escalation of tension", adding: "it is unprecedented, and of course it requires special attention and special measures."