ISTANBUL

The Swedish navy is detecting Russian submarines in the Baltic Sea on an “almost weekly” basis, a senior naval commander said, The Guardian reported on Saturday.

Capt. Marko Petkovic, the Swedish navy’s chief of operations, said sightings of Russian vessels had become “very common” and had increased in recent years as Moscow expands and modernizes its fleet.

“Russia is continuously reinforcing its presence,” Petkovic said, noting that Sweden expects even more submarine activity once a ceasefire or armistice is reached in Ukraine.

“You can only assess, and we do assess, that Russia will reinforce its capabilities in this region.”

The Baltic Sea has seen a rising number of security incidents, including suspected drone activity, alleged sabotage of underwater infrastructure, and the movement of ageing oil tankers forming Russia’s so-called “shadow fleet.”

Last month, the UK defense secretary said a Russian spy ship had entered British waters and shone lasers at military pilots, warning that the UK faced a “new era of threat” from hostile states.

Sweden recently hosted one of NATO’s largest anti-submarine warfare drills in the region, Playbook Merlin 25, bringing together nine nations, including Germany, France, and the US, to practice hunting submarines in the Baltic’s challenging underwater terrain.

Petkovic said the seabed’s steep underwater terrain near Sweden provides submarines with more opportunities to hide, complicating detection efforts.

Petkovic said Russia is producing roughly one Kilo-class submarine per year in St. Petersburg and the Kaliningrad exclave, which sits between Poland and Lithuania.

He described Russia’s naval activity as a “deliberate and constant modernization program.”

He also warned that Russia’s shadow fleet, composed of civilian-flagged oil tankers transporting crude from Russia, could pose risks if used to launch drones or conduct covert operations.

“The shadow fleet in itself is not a military problem, but the shadow fleet could affect our nations from a military perspective,” he said.

Petkovic highlighted that underwater infrastructure in the Baltic Sea, particularly in Sweden, Norway, Finland, Estonia, and Lithuania, remains vulnerable due to challenging underwater conditions, including low visibility, varying salinity, and temperature differences.

These countries depend heavily on maritime routes for communication and supplies.

However, he said NATO’s increased vigilance has had a deterrent effect. Since the launch of Operation Baltic Sentry in January, “we haven’t seen any cable incidents in this region at all,” he noted.

“It shows that the alliance works,” he said.