A Chinese naval flotilla including two destroyers sailed through waters near Japanese islands on Tuesday, further fuelling tensions, in what one commentator said was a sign of things to come.

The seven warships --- at least one of which was capable of firing missiles -- passed close to territory internationally recognised as Japanese. The two nations are already embroiled in a bitter wrangle over a separate island chain.

A defence ministry spokesman said it was the first time the Chinese navy had used the passage, but Ryo Sahashi, a specialist in international politics at Kanagawa University said it would not be the last.

"Generally speaking, China acts in accordance with its government's claims," he said.

"It is likely that we will see similar acts repeated in the future," he said, while cautioning it was too early to assess the full meaning of the move.

China's increasingly well-funded navy is somewhat hemmed in by the long chain of Japan's Okinawan islands and must pass relatively near 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.

A defence ministry spokesman said the seven Chinese naval ships had been involved in exercises in the Pacific Ocean, and "they passed through a wider space between Okinawa island and Miyako island on their way out" on October 4.

"They passed through the narrow strait on the way back, and this is the first time we have confirmed that they passed through this gap," the spokesman said.

He said a Japanese spotter aircraft had logged the vessels 49 kilometres south-southeast of Yonaguni island at 7:00 am (2200 GMT Monday).

The flotilla comprised 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.

At one point the vessels entered contiguous waters, a ministry spokeswoman said.

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 a state is allowed to exercise control to "prevent infringement of its customs, fiscal, immigration or sanitary laws and regulations within its territory or territorial sea", UNCLOS says.

"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," Defence 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."

He said these Chinese exercises had been going on since 2008.

"They have gradually expanded the area of activity but we cannot tell what intentions lie behind that," Morimoto told reporters.

The move comes after days of relative calm in a long-running dispute 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.

The dispute flared in August after landings by nationalists from both sides and the subsequent nationalisation of the islands by Tokyo.

Large public protests rocked Chinese cities, forcing Japanese firms to shutter or scale back their operations.

Two-way trade, worth well in excess of $300 billion last year, is starting to show signs of impact from the dispute. Automaker Toyota was reported Tuesday to be planning to temporarily close a factory in China because of falling demand for Japanese goods.