A top aide to President Vladimir Putin has laughed off the sanctions imposed by the US, saying the only thing he likes about America is Tupac, and he "doesn't need a visa" to listen to rap music.

Vladislav Surkov, one of the seven Russian officials slapped with White House sanctions, told a Russian newspaper being on America's blacklist is a "big honour" for him.

He added: "The only things that interest me in the US are Tupac Shakur, Allen Ginsberg, and Jackson Pollock. I don’t need a visa to access their work. I lose nothing."

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Similarly, Russia's Deputy Prime Minister Dmitry Rogozin, tweeted the sanctions appeared to have been drawn by "some pranksters" on behalf of "comrade" Obama.

Rogozin tweeted: "Comrade Obama... What will you do with those who have neither accounts nor property abroad? Or didn’t you think of that?"

The incendiary comments come shortly after Kremlin-backed television presenter Dmitry Kiselyov warned Moscow could turn the US "into radioactive ash" in a nuclear attack.

"Russia is the only country in the world realistically capable of turning the United States into radioactive ash," Kiselyov said standing in front of a large screen depicting a mushroom cloud produced by a nuclear explosion.

"Even if people in all our command posts after an enemy atomic attack cannot be contacted, the system will automatically fire our missiles from mines and submarines in the right direction," he added.

Yesterday, President Barack Obama authorised the US Treasury Department to freeze dollar-denominated assets of seven Russian individuals in the wake of the Crimean referendum, which saw an overwhelming majority vote 'yes' to joining the Russian Federation.

European foreign ministers also imposed sanctions against 21 Russian and Ukrainian officials deemed responsible for the unrest in the region, including Sergey Aksyonov, the prime minister of Crimea. Brussels and Washington have branded the referendum illegal and in breach of international law.

President Obama also warned more sanctions would follow if Russia did not change course and “de-escalate” the situation after the Russian leader paved the way for Crimea’s annexation by formally recognising it as an independent state.

Speaking in a televised address earlier today, President Putin insisted that Russia and Crimea are "inseparable" and reiterated that Sunday's referendum took place "in full accordance with international law".

Meanwhile, vice-president Joe Biden has landed in Warsaw to meet with the leaders of four Nato allies – Poland and the three Baltic states, which have all expressed alarm about the possible future scope of Russian aggression.