A powerful armada of 28 Russian naval ships was sighted sailing from the Sea of Okhotsk to the Sea of Japan, passing through the Soya Strait in the waters off Hokkaido, the Defense Ministry reported Sept. 3.

The ministry said the number of Russian naval vessels sailing through the strait is a record high since the Cold War. The ships did not engage in any "dangerous activities" and did not enter Japanese territorial waters.

The Soya Strait, also known as the La Perouse Strait, divides the Russian island of Sakhalin and Japan's northernmost Hokkaido.

Between around 9:30 p.m. on Sept. 1 and around 4 p.m. on Sept. 2, Maritime Self-Defense Force ships and a patrol aircraft confirmed the flotilla's movement in waters about 210 kilometers northeast of Cape Soya, Japan’s northernmost point in Wakkanai, Hokkaido.

On Aug. 28, the Russian defense ministry announced that 40 of its naval vessels and other ships had been in operation in the Sea of Japan and the Sea of Okhotsk based on its exercise schedule.

Defense Minister Itsunori Onodera has expressed concerns about such Russian movements, including the military buildup on four islands off eastern Hokkaido, which are at the heart of a long-standing territorial dispute between Japan and Russia.