Russian frigate Admiral Gorshkov – the first of a four-ship convoy – fired a 21-gun salute after entering Havana harbor, which was answered by the Cubans with cannon fire from an 18th-century colonial fort built by the Spanish to guard the port.

The Gorshkov is one of the Russian Navy’s most modern ships, and was followed by the nuclear-powered submarine Kazan, a rescue tug, and an oil tanker.

Onlookers and fishermen lined the seafront to watch the vessels arrive in the harbor. A CNN team on the ground saw members of the small Russian community in Cuba and Russian diplomats carrying national flags to welcome the crews.

Some of the Cubans present told CNN they had never seen a submarine enter the bay of Havana before.

The four Russian ships are now docked in berths usually occupied by cruise ships.

It marks the largest show of force by the Russians with their longstanding ally Cuba in many years. The US assesses that the Kazan does not have nuclear weapons on board, a US official said.

The vessels will carry out a five-day official visit to the Caribbean island – a show of Russian force just 90 miles from Florida as tensions rise between the US and Russia over the war in Ukraine.

Cubans will be permitted to tour the frigate following the arrival of the convoy of ships, a Russian diplomatic source told CNN.

The Russian diplomat told CNN that starting Thursday, “the general public” in Cuba will be allowed to tour the Gorshkov frigate for four hours each day for three days. Military analysts believe it is capable of long-range missions, anti-submarine warfare, and carrying surface-to-surface and surface-to-air missiles, among other weapons systems.