Satellite images show Russia fortified a port against Ukrainian drone boats. One broke through underwater and exploded.

• Ukraine said Monday that it carried out an underwater drone attack on a Russian submarine in port.
• New satellite imagery shows damage at the Novorossiysk port following an explosion.
• The imagery also shows that Russia had tried to fortify the port against Ukrainian attacks ahead of time.

Newly captured satellite imagery shows the aftermath of a Ukrainian drone attack that targeted a Russian submarine at a naval base on the Black Sea.

The new imagery, captured on Tuesday by the US spatial intelligence firm Vantor and obtained by Business Insider, shows damage to a section of a quay at the port of Novorossiysk next to a Kilo-class submarine.

Ukraine's internal security agency said on Monday that it used underwater drones to strike a Russian submarine at the port in a first-of-its-kind attack. Kyiv published footage of the operation, which caused a large blast in the port, and said it damaged and disabled the boat.

Russian state media, citing the Black Sea Fleet, said later on Monday that the attack failed to damage a submarine.

The satellite imagery does not appear to reveal any visible damage to a submarine; however, there could be some beneath the surface, making it difficult to determine the success of the operation.

Russia's Kilo-class submarines — diesel-electric boats that have been in service since the 1980s — are used to carry out Kalibr cruise missile strikes against Ukraine, making them a high-value target for Kyiv.

The new imagery also reveals floating barriers at the entrance of the port, a tactic that Russia has used to protect its warships and infrastructure from Ukrainian naval drone attacks. However, this kind of defense is primarily aimed at surface threats, as the underwater drone was still able to enter the port and cause an explosion.

Ukraine has used its fleet of explosive-packed naval drones and long-range missiles to damage and destroy dozens of Russian warships and vessels since the start of the full-scale invasion.

This asymmetric campaign has forced Russia to relocate its Black Sea Fleet away from its long-held headquarters in the occupied Crimean peninsula to Novorossiysk, on the other side of the region. However, Ukraine continues to demonstrate that it can also target this port.

The attack, the latest against the Black Sea Fleet, appears to signal a new chapter in drone warfare. Ukraine has mainly relied on surface naval drones to target Russian warships.

The use of an underwater drone, compared to a slow-moving mine or torpedo, suggests a significant expansion of Ukraine's capabilities that could pose a new threat to the Black Sea Fleet.

Conflict analysts at the Institute for the Study of War, a US think tank, wrote in a battlefield assessment on Monday that Russia had docked its Kilo-class submarines in Crimea but moved them to Novorossiysk several years ago because of Ukraine's strike campaign.

The recent underwater drone attack "shows that Ukrainian forces continue to modernize and optimize their unmanned capabilities such that Ukraine can strike Russian military targets at a range that Russian forces previously thought safe," the analysts said.