A Russian warship patrolling in waters close to a U.S. nuclear missile submarine base has been warned it is operating in an unsafe manner by the coastguard.

The Viktor Leonov was spotted off the coast of South Carolina and Georgia and has regularly been seen in international waters along the eastern coast since 2015.

On Sunday the Charleston coastguard issued a maritime safety information bulletin saying the ship had 'erratic movements', reported the Washington Times.

Russian warship the Viktor Leonov has been warned it is operating in an unsafe manner by the coastguard in Charleston, South Carolina (file picture of the ship in Havana, Cuba, in 2015)

As well as being close to the submarine base, the Viktor Leonov, Vishnya-class intelligence ship is also suspected of spying on undersea internet cables.

The coastguard's full safety bulletin explained the 'unsafe operation' and also warned other vessels to 'use extreme caution' when close to the Viktor Leonov.

It read: 'The United States Coast Guard has received reports indicating that the RFN Viktor Leonov (AGI-175) has been operating in an unsafe manner off the coast of South Carolina and Georgia.

'This unsafe operation includes not energizing running lights while in reduced visibility conditions, not responding to hails by commercial vessels attempting to coordinate safe passage and other erratic movements.'

When not off the eastern coast, the warship is also found patrolling in Cuba and Trinidad and Tobago.

A defense official said the US Navy's USS Mahan destroyer was operating close to the Russian ship, reported CNN.

The coastguard warned that the ship was 'not responding to hails by commercial vessels attempting to coordinate safe passage and other erratic movements' (file picture)

The ship, which carries high-tech surveillance equipment and weaponry, AK-630 rapid-fire cannons and surface-to-air missiles, was also spotted just 70 miles off the coast of Delaware in February 2017.

At the time an official said: 'It's not a huge concern, but we are keeping our eyes on it'.

THE RUSSIAN SPY VESSEL VIKTOR LEONOV The Vishnya class intelligence-gathering ship went into service in the Black Sea in 1988 before it was transferred seven years later to the northern fleet. It is named after Second World War Soviet sailor Viktor Leonov. Ship measures 300 feet long and 47.5 feet wide. It has a crew of 200 sailors carries high-tech electronic surveillance equipment and weaponry, AK-630 rapid-fire cannons and surface-to-air missiles Advertisement

The intelligence ship also patrolled near the U.S. nuclear missile submarine base in Kings Bay, Georgia, in 2014.

The Department of Defense suspected that may have been part of an intelligence-gathering operation.

In a throwback to the Cold War, the spy ship also caused a stir after unexpectedly docking in Havana on the eve of historic talks between the U.S. and Cuba the following year.

There was nothing stealthy about the arrival of the Leonov, which was moored to a pier in Old Havana where cruise ships often dock.

But the visit was not officially announced by Cuban authorities. The timing also raised eyebrows as it came on the eve of historic U.S-Cuba talks aimed at normalizing diplomatic relations.

U.S. officials in Washington played down the presence of the Russian vessel, saying it was perfectly legal and not at all out of the ordinary.

'It's not unprecedented. It's not unusual. It's not alarming,' a defense official told AFP news agency.