The Russian navy is stocking up on one of its best defensive weapons against Ukraine — military-trained dolphins, according to a new intelligence report.

Satellite imagery shows the number of floating mammal pens in the harbor of its main port base in annexed Crimea nearly doubling from April to June, indicating Russia is training more combat dolphins to counter Ukrainian forces, according to the UK intelligence report.

The bottlenose dolphins helping to safeguard the entry to the port of Sevastopol in Russian-occupied Crimea are “highly likely intended to counter enemy divers,” British authorities said last week.

The new satellite images show “at least four layers of nets and booms across the harbor entrance. In recent weeks, these defences have highly likely also been augmented by an increased number of trained marine mammals,” the intelligence report said.

“Imagery shows a near doubling of floating mammal pens in the harbor which highly likely contain bottle-nosed dolphins,” it added.

The Russian navy began investing in major advancements to the Black Sea Fleet’s main base in Sevastopol last summer.

The navy has also used beluga whales and seals for missions in Arctic waters, both of which have heavy layers of fat to keep warm and are better protected against the cold than bottlenose dolphins.

Earlier this year, the US Naval Institute reviewed the imagery from the Sevastopol harbor and concluded that two dolphin pens were moved to the base in February.

The militarized mammals may have been tasked with counter-diver operations to prevent Ukrainian special-ops forces from entering the harbor underwater to sabotage warships, according to the report.

Russia has a long history of using marine mammals in times of conflict.

During the Cold War, the Soviet Navy developed dolphin training in the Black Sea. The use for them eventually faded till the annexation of Crimea in 2014.

The recent additional dolphin pens come as a whale suspected to be a spy trained by the Russian navy appeared off the coast of Sweden last month.

The beluga whale was nicknamed Hvaldimir by locals, a combination of the Norwegian word for whale — hval — and Russian President Vladimir Putin.

The supposed spy first grew to fame after he was discovered wearing a human-made harness off the coast of Norway in 2019 and has spent over three years slowly moving down the Norwegian coastline.

The great white whale recently picked up speed, moving from the Norwegian coast to Sweden late last month.

Scientists believe that Hvaldimir has not seen another beluga since he arrived in Norway in April 2019.

When Hvaldimir was first spotted in the Norwegian Arctic, marine biologists removed the human-made harness from him.

The harness featured a mount suited for an action camera and the words “Equipment St Petersburg” printed on its plastic clasps.

Russian officials have not commented on Norwegian speculation that Hvaldimir could be a Russian spy.