Japan's Defence Ministry says Chinese warships have been spotted in waters near a Japanese island, further stoking tensions with Beijing over a disputed archipelago.
The ministry says two destroyers, two frigates, two submarine rescue ships and a supply ship had been seen moving north from the Pacific Ocean to the East China Sea near the island of Yonaguni on Tuesday morning.
The island is just outside Japan's territorial waters, but internationally acknowledged as Japanese, AFP reports.
The announcement comes in the midst of 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.
China's 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, 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.
Two-way trade, worth well in excess of $US300 billion last year, is starting to show signs of impact from the spat, with carmaker Toyota reported to be planning to temporarily close a factory in China because of falling demand for Japanese goods.