Nuclear threat heightened after Russian warship destroyed

The dramatic sinking of Russia's lead warship could be the catalyst that pushes Putin to deploy nuclear weapons, the director of the CIA says.

Russian forces have faced a string of major setbacks since invading Ukraine in late February. The latest of which was the warship sinking in the Black Sea late on Thursday.

Ukraine claimed responsibility for sinking the Moskva, saying the Soviet-era flagship of Russia's Black Sea fleet was struck by one of its missiles.

The vessel sank as it was being towed to port, Russia's defence ministry said.

Among those concerned about Putin starting a nuclear war is the CIA Director, who spoke at the Georgia Institute of Technology about the setbacks Putin has been dealt and the "potential desperation" they have led to.

Recently, Russian forces – which have suffered heavy losses – withdrew from the capital Kyiv.

William Burns, who served as the American ambassador to Russia from 2005 to 2008, said the threat of Russia using tactical or low-yield nuclear weapons in Ukraine should not be taken lightly.

"Given the potential desperation of President Putin and the Russian leadership, given the setbacks that they've faced so far militarily, none of us can take lightly the threat posed by a potential resort to tactical nuclear weapons or low yield nuclear weapons,” he said.

While there has been "rhetorical posturing" from the Kremlin about putting the world's largest arsenal of nuclear weapons on high alert, Mr Burns said there hasn't been "a lot of practical evidence" of deployments of military dispositions that are of concern.

Tactical and low-yield nuclear weapons refer to those designed for use on the battlefield, of which some experts estimate Russia has about 2000 that can be delivered by air, naval and ground forces.

Mr Burns also said Putin has become more isolated as the war progressed.

“His circle of advisors has narrowed and in that small circle it has never been career-enhancing to question his judgment or his stubborn, almost mystical belief that his destiny is to restore Russia's sphere of influence,” Burns said, according to CNN.

Air raid sirens ring through Ukraine after 'high profile' loss

Following the sinking of the warship, explosions were heard throughout Ukraine, the most significant in the country's capital region – the first time since Russian forces pulled back.

More than 500 crew members were on the Russian missile cruiser and were evacuated after ammunition on board exploded, the Russian defence ministry said.

The loss of the ship comes as Russian naval forces continue its bombardment of Ukrainian cities on the Black Sea.

Just after midnight on Friday, air raid sirens sounded in all regions of Ukraine.

The sirens continued blaring in the eastern regions of Luhansk and Zaporizhzhia even when they went quiet in the other regions.

Russia is investigating the cause of the fire on the Moskva, while the US did not have enough information to determine whether it was hit by a missile.

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Regardless of what caused Moskva to perish, it is an undeniable setback for Russia.

If Ukraine did hit the ship with a missile, the attack will go down in history as one of the highest-profile naval attacks so far this century, Reuters noted.

Russia started its vicious assault on Ukraine in an attempt to dissuade its neighbour from joining NATO.

The invasion has now pushed Finland, which shares a border with Russia, and nearby Sweden to consider joining the military alliance.

On Thursday, Moscow warned NATO if Finland and Sweden join, Russia would deploy nuclear weapons and hypersonic missiles in a Russian enclave on the Baltic Sea, in the heart of Europe.

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