Japanese navy shadows Russian Vishnya-class spy ship near Tsushima

A Russian Navy intelligence-gathering ship sailed southwest through the Tsushima Strait between Japan and South Korea on Oct. 27 and 28 and headed into the East China Sea, Japan’s Joint Staff Office said.

The Joint Staff identified the vessel as a Vishnya-class intelligence collection ship and released a map showing its hull number, 535. That number belongs to the Kareliya, a signals intelligence ship of Russia’s Pacific Fleet based in Vladivostok. Japan’s Maritime Self-Defense Force tracked it with the minesweeper Hirashima of the 3rd Mine Warfare Squadron, based in Sasebo, and a P-1 maritime patrol aircraft of Fleet Air Wing 4 flying from Atsugi.

The map shows the Kareliya passing east of Tsushima Island, which sits in the middle of the strait, before continuing southwest past the Goto Islands off Kyushu toward the open waters of the East China Sea. The Joint Staff did not say whether the ship entered Japan’s territorial waters or contiguous zone, the band of sea up to 24 nautical miles (44 km) from the coast, during the transit.

Vishnya-class ships, known in Russia as Project 864, are built to collect radio, radar and other electronic signals, letting the Russian Navy listen in on military communications and map the sensors of foreign forces. Poland’s Stocznia Północna shipyard in Gdańsk built seven of them for the Soviet Navy in the 1980s, and all remain in Russian service. The 91.5 m (300-foot) ships have a top speed of about 16 knots.

The Kareliya is a familiar sight to the Japanese military. In January, Japan tracked it as it passed through the contiguous zones around Yonaguni and Miyako Islands before heading into the Pacific, and in February 2025 Japan reported that it spent more than a week operating near Okinawa and Kyushu. The ship has also operated far from Japan, including off Hawaii, where it was spotted in 2021 13 nautical miles west of Kauai, home to the U.S. Navy’s Pacific Missile Range Facility.

The Tsushima Strait is one of the main routes Russian Pacific Fleet ships use to sail between the Sea of Japan and the East China Sea, and Japan publishes a release each time it detects a Russian or Chinese warship passing through the waterways around its islands. The ship was commissioned in 1986 and returned to the fleet in 2017 after a three-year repair and upgrade.