Russian submarines are coming off the Swedish coast more and more frequently. But they are not the only danger in the Baltic Sea.
December 7, 2025, 7:00 a.mDecember 7, 2025, 7:00 a.m
Thomas Wanhoff / t-online
The Swedish Navy deals with Russian submarines traveling in the Baltic Sea almost every week. Sightings are common, but the number has increased in recent years, said Swedish naval captain and operations manager Marko Petkovic to the British Guardian.
Russian submarines have recently been appearing more frequently in the Baltic Sea.Image: keystone
If there is a ceasefire in Ukraine, the Swede expects even more patrols by the Russian navy. In the Baltic Sea there are repeated incidents involving Russian warships, fighter jets, transport aircraft, but also suspicious ships such as the oil tankers from Putin’s shadow fleet.
On October 15, 2025, the Swedish Navy reported that a Russian Kilo-class submarine (Project 636.3) had entered the Baltic Sea via the Great Belt. It was pursued in Kattegat by Swedish fighter planes and corvettes. In November, the British military reported that a Russian spy ship was traveling in its waters and was targeting pilots with a laser.
“Russia produces a submarine on the Baltic Sea every year”
Sweden has just taken part in a NATO exercise, Playbook Merlin 25, which focused on anti-submarine warfare. Germany was also there. It was no coincidence that the Baltic Sea was chosen as the training region.
The potential danger is significant. According to Petkovic, Russia produces one Kilo-class submarine every year in St. Petersburg and the Kaliningrad enclave. This is also where the Russian Baltic Fleet is located. Although the Russian Kilo boats do not have a nuclear reactor, they can operate very quietly with their electric and diesel engines. This is particularly advantageous in the rugged waters off Sweden, where submarines can hide between undersea rock formations.
Shadow Fleet could serve as a drone transporter
Russia is pursuing a constant modernization program for its submarines, says the Swedish naval captain. “As soon as a ceasefire or a peace agreement is reached in Ukraine, one can only assume – and we also assume this – that Russia will strengthen its capacities in this region,” said Petkovic. “Against this background, the [schwedische] Marine continually grow and focus on the bigger picture.”
But he also sees another danger: the ships of the Russian shadow fleet. “The Shadow Fleet itself is not a military problem, but it could affect our nations from a military perspective,” Petkovic said. Not only could they transport oil, but they could also serve as a launch base for drones.
A tanker that is said to belong to the Russian shadow fleet.Image: keystone
NATO has increased its presence in the Baltic Sea, with more reconnaissance flights and radar surveillance. This has already led to a reduction in suspected Russian sabotage. “We have not seen any cable incidents in this region at all,” said Petkovic.
Ultimately, the NATO presence is also a deterrent that works. “Regardless of whether these incidents were state-sponsored or due to crew incompetence or anything in between, this has raised the awareness of merchant vessels that they should be a little more careful when navigating our regional waters,” said Petkovic.
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