Sunak was 'briefed' after Russian submarine detected near UK coast

• Russian submarine passed by Britain before going on to Havana, Cuba this week 

Rishi Sunak was given a 'secret briefing' after a Russian nuclear submarine was spotted off the coast of Scotland earlier this month, it has been revealed.

The Prime Minister and Defence Secretary Grant Shapps were alerted to the detection of a Russian Yasen-class submarine after a RAF surveillance plane trailed its movements along the west coast of Ireland to Scotland.

The 13,800-tonne submarine Kazan passed by Britain's nuclear naval base in Faslane without crossing into British waters, prompting swift reports back to the Permanent Joint Headquarters in Northwood, London, The Express reported.

Kazan was picked up by an RAF Poseidon P8 anti-submarine aircraft on June 5, expected to head on to Venezuela and Guyana where British ships had recently been conducting patrols.

It ultimately churned into Havana harbour on Wednesday, a stopover the U.S. and Cuba said posed no threat but which was widely seen as a Russian show of force as tensions rise over the Ukraine war.

Russian Yasen-class submarine 'Kazan' passed through international waters near the UK

Rishi Sunak (pictured in Italy on June 14) was notified about the appearance of the sub

Military commanders were reportedly concerned that the Kazan could be looking for vulnerabilities around the UK, The Express reported.

A Royal Navy spokesperson said: 'The Royal Navy routinely monitors UK territorial waters and the adjacent sea areas to ensure compliance with maritime law, to deter malign activity and to protect our national interests.'

When the submarine came just 25 miles from the United States this week, White House national security adviser Jake Sullivan said the US would also remain vigilant.

Kremlin spokesman Dmitry Peskov said there was no reason to worry, suggesting such exercises were common practice.

'This is a normal practice for all states, including such a large maritime power as Russia,' Peskov told reporters. 'So we don't see any reason to worry in this case.'

Cuba's foreign ministry said the vessels carried no nuclear weapons, an assertion echoed by U.S. officials.

Russian pro-war Telegram channels boasted that Kazan has 'guided missile weapons' on board as it passes close to the American coastline, around 25 miles east of Florida.

Kazan, half submerged with its crew on deck, and the Admiral Gorshkov frigate sailed into Havana harbor on Wednesday after conducting 'high-precision missile weapons' training in the Atlantic Ocean.

The drills involve hitting targets from a distance of more than 370 miles, Russia's defence ministry said in a statement, and follow an exercise in anti-aircraft fire.

Both the Admiral Gorshkov and the Kazan are normally key vessels in Putin's nuclear strike force.

Cubans and tourists on holiday in Havana viewed the ships from a distance, and dozens formed a queue under the hot Caribbean sun for the opportunity to go aboard the frigate.

'The United States need not worry,' said Havana resident Ariel Vera, a 55-year-old state worker who was among the first in line.

'Cuba is a country of peace and our Russian friends are coming on a friendly visit.'

The Russian vessels are expected to remain in Havana until Sunday, Russia's defence ministry has said.

A convertible American classic car drives by as people watch Kazan in port on June 12

People with Russian flags look at the Russian nuclear-powered submarine Kazan in Havana

The Kazan's port call on Wednesday coincided with a meeting in Moscow between Cuba's Foreign Minister Bruno Rodriguez and his Russian counterpart Sergei Lavrov, as the two former Cold War allies further tighten their links.

During the meeting, Rodriguez expressed his government's "rejection of the expansion of the North Atlantic Treaty Organization (NATO) towards the Russian border," which he said "led to the current conflict in Europe, and especially between Moscow and Kyiv," according to a Cuban foreign ministry statement.

He also called for "a diplomatic, constructive and realistic solution" to the crisis.

The arrival of Kazan was seen in the West as reminiscent of the days of the Cold War and the Cuban missile crisis when the US faced off against Cuba and the USSR.

Relations deteriorated until the 1962 Cuban missile crisis - a 13-day standoff considered the closest the world came to nuclear war when the US learned that the USSR had secretly begun missile shipments to Cuba.

The crisis was resolved diplomatically, with the US secretly removing its missiles from Turkey and Italy as the USSR agreed to halt work on missile sites in Cuba.

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