TOKYO: Chinese warships, including two destroyers, were spotted in waters near a Japanese island on Tuesday, the defense ministry in Tokyo said, further stoking tensions with Beijing over a disputed archipelago.

“A Japanese aircraft spotted seven Chinese naval ships in waters 49 kilometers south-southeast of Yonaguni island at 7 a.m. [6 a.m. in Manila],” a ministry official said.

Yonaguni is an inhabited territory internationally acknowledged as Japanese.

The ministry said that the ships were two destroyers, at least one of which had missile capacity, two frigates, two submarine rescue ships and one supply ship.

“They were moving north, from the Pacific Ocean to the East China Sea,” the spokesman said.

“They were in contiguous waters, 44 kilometers southwest of Naka-nokamishima,” a defense ministry spokesman said separately.

Contiguous waters lie just outside territorial waters and are governed by international maritime law.

“At this time, we are not seeing such acts as helicopters flying from these naval ships and approaching toward our nation or [the ships] sailing within our territorial waters,” Defense Minister Satoshi Morimoto told a press briefing.

“We are continuing to be on alert and maintaining surveillance of the area waters with aircraft and ships. We will continue to carefully collect information about the movement of the Chinese naval vessels.”

The announcement comes after days of relative calm in a long-running dispute between Japan and China over the sovereignty of a small group of islands in the East China Sea.

Tokyo and Beijing are at loggerheads over the Senkaku islands, which are administered by Japan, but claimed by China, which calls them the Diaoyu islands.

Over the last few weeks Chinese government ships—maritime surveillance ships and fisheries patrol vessels—have repeatedly sailed close to the archipelago, but the country’s armed forces have apparently stayed away.

China’s increasingly well-funded navy is somewhat hemmed in by the long chain of Japan’s Okinawan islands and must pass near to them to get into the Pacific from the East China Sea.

However, there are gaps between the islands that allow vessels to stay well away from Japan’s contiguous zones, an area that extends a further 12 nautical miles beyond the 12 nautical miles of territorial waters.

Under the United Nations Convention on the Law of the Sea (Unclos), to which both Japan and China are signatories, foreign vessels, including military ships, have the right to use the contiguous zone.

But states are permitted to exercise control to “prevent infringement of its customs, fiscal, immigration or sanitary laws and regulations within its territory or territorial sea,” Unclos says.

Reports over the weekend said that Japan and the United States were considering a joint military drill to simulate retaking a remote island from foreign forces.

The exercise, part of broader joint maneuvers to start in early November, would use an uninhabited island in Okinawa, Jiji Press and Kyodo News reported.

The drill would involve Japanese and US troops making an amphibious and airborne landing using boats and helicopters, Kyodo said.

The report came after months of vociferous disagreements over the Senkaku islands, which flared in August and September with landings by nationalists from both sides and the subsequent nationalization of the islands by Tokyo.