The photo shows one of the seven Chinese naval vessels spotted entering the East China Sea en route to the Diaoyu Islands on Oct. 16, 2012, according to Japanese media. [Photo/Sina]

Japan's Defense Ministry says it has spotted early Tuesday seven Chinese naval vessels appear in waters 49 kilometers south-southeast of Yonaguni Island, Japan's westernmost inhabited island. [Full coverage: Diaoyu Islands dispute]

The spotted Chinese warships included two destroyers, according to the ministry.

"They were moving north, from the Pacific Ocean to the East China Sea," a ministry official said.

"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."

China has kept sending fishery and surveillance ships to patrol the waters surrounding the Diaoyu Islands, since the "purchase" of China's Diaoyu Islands by the current Japanese administration.

Previously, China's five fishery patrol ships were sent to the waters off the Diaoyu Islands during the National Day holiday.

The island row has severely harmed the diplomatic ties between the two countries, brining the tension to a flashpoint.