Russian surveillance ship Kareliya (535) seemingly concluded a two-week surveillance mission around Japan’s southwest region Monday, its time in the area overlapping with a Chinese surveillance ship, officials from the island country said.

Kareliya sailed Monday through the contiguous zone south to east of Okinawa toward the Philippine Sea after operating in the area since Jan. 12, according to Japan’s Joint Staff Office. Saturday – two days before the Russian ship departed – a Chinese Dongdiao-class surveillance ship sailed between Miyako Island and Okinawa to enter the Philippine Sea. Then, on Monday, a Russian IL-20 Electronic Intelligence (ELINT) aircraft flew off the eastern coasts of Hokkaido and Honshu.

“The Chinese and Russian militaries have continued to engage in active operations in the sea and airspace surrounding our country since the beginning of this year, utilizing intelligence-gathering ships and aircraft, among other assets, Japan Defense Minister Shinjiro Koizumi said in a Monday post on social media site X. “Given the characteristics of the ships and aircraft involved in these activities, it is conceivable that these operations are intended for some form of intelligence gathering.”

The U.N. Conventions of Law of the Sea defines the contiguous zone as a band of water that starts from the 12-nautical mile limit of a nation’s territorial sea and ends 24 nautical miles from a country’s baseline. Nations have limited rights in this area, allowing them to take action only against infringement of its customs, fiscal, immigration or sanitary laws and regulations within its territory or territorial sea. As such, ships may freely pass through the contiguous zone, which Russian and Chinese surveillance ships have frequently done around Japan. Many countries consider the sailing of a military or surveillance ship within 24 miles of its coast, unless the waters are international straits, as provocative.

Japan’s Joint Staff Office and its maritime self-defense force began tracking Kareliya on Jan. 7 when it sailed southwest through the Tsushima Strait. The Russian surveillance ship was within proximity of Japan’s southwest region Jan. 12, where it operated for two weeks.

Over the last week, Japan Maritime Self-Defense Force (JMSDF) sighted Kareliya sailing west around 70 kilometers east of Okinawa, cruising the waters east to southeast of Okinawa Island, including the contiguous zone. Then, From Friday to Saturday, Kareliya navigated the waters southeast of Okinawa to northwest of Kume Island. On Sunday, Kareliya began its transit northeast through the Tsushima Strait to enter the Sea of Japan, according to the release. The Russian surveillance ship is believed to be returning to its home port of Vladivostok.

Japan dispatched multiple assets to conduct surveillance and intelligence gathering on Kareliya, including most recently destroyer JS Ikazuchi (DD-107), fleet oiler JS Mashu (AOE-425), minesweeper JS Takashima (MSC-603) and P-3C Orion Maritime Patrol Aircraft.

People’s Liberation Army Navy Dongdiao-class surveillance ship Beijixing (791) was also in the region Saturday, sailing southeast around 120 kilometers northeast of Miyako Island, according to a separate news release from Japan officials. Beijixing then sailed southeast between Okinawa and Miyako Island and into the Philippine Sea. Mashu and a JMSDF P-3C Orion patrol aircraft shadowed the PLAN ship.

Additionally on Monday, a Russian IL-20 ELINT aircraft flew in from the Russian continent and crossed the Sea of Okhotsk before entering the Pacific Ocean. The IL-20 then flew south to the coast of Honshu’s Fukushima Prefecture before turning back to cross the Sea of Okhotsk into the Sea of Japan.

The IL-20 entered Japanese territorial airspace, though the boundary lines cover the islands of Iturup, Kunashir, Shikotan and the Habomai Islands which have been held by Russia but claimed by Japan since the end of World War II.

In response, fighter aircraft from the Japan Air Self-Defense Force (JASDF) Northern Air Defense Command were scrambled, Japan said.

Sovereign airspace is restricted to 12 nautical miles from a country’s baseline, but a number of countries – including Japan – maintain an Air Defense Identification Zone that extends beyond 12 nautical miles to identify approaching aircraft in international airspace. These ADIZs are not recognized under international law. Standard practice for most countries is to have fighters intercept and escort the aircraft through the ADIZ until the aircraft leaves the area.

“The Ministry of Defense and the Self-Defense Forces will continue to maintain the utmost vigilance in monitoring and surveillance with a strong focus on the activities of the Chinese and Russian militaries in the sea and airspace surrounding our country, at any time and under any circumstances,” Koizumi concluded in his X post.