MOSCOW, Feb 24 (Mirror) - Vladimir Putin has appeared to threaten nuclear strikes if any country tried to attack Russia in retaliation in a terrifying speech.

The president said the “consequences” of any attempt to strike back following the country's invasion of Ukraine would provoke a response “never seen in history”.

In an address to the UK, Prime Minister Boris Johnson said that "diplomatically, politically, economically – and eventually, militarily – this hideous and barbaric venture of Vladimir Putin must end in failure".

Analysts believe the threat of deploying nuclear weapons should the Russian Army be attacked by forces outside of Ukraine was implicit in President Putin's speech.

Broadcast live on television at 5.45am Moscow time, President Putin said: "Whoever tries to impede us, let alone create threats for our country and its people, must know that the Russian response will be immediate and lead to the consequences you have never seen in history."

“All relevant decisions have been taken. I hope you hear me.”

Officials have said an attack on a military unit in Podilsk, outside Odessa in Ukraine, killed six people and wounded seven.

Russian tanks have have also crossed the Ukrainian border via Belarus.

NATO has now announced that it will take additional steps to strengthen the alliance's deterrence and defence and officials said it would hold an emergency summit of its 30 member nations on Friday.

President Putin's chilling address was a stark reminder to the West of Russia's nuclear power.

"No one should have any doubts that a direct attack on our country will lead to the destruction and horrible consequences for any potential aggressor," he said in his speech that acted as a declaration of war on Ukraine.

The invasion followed shortly after, leading to widespread horror and anguish as the human impact of the war began to take its toll.

Nuclear options represent the most drastic weapon in the armoury of superpowers, and the decision to use them carries the gravest of consequences.

While Russian nuclear weapons have the range to hit the UK, the possibility of nuclear weapons being used remains a long way off.

That's because the devastation it could cause would outweigh any potential benefit from the mass destruction.