China complained to Japan early this month about Japanese fishing boats allegedly "trespassing" in its territorial waters near a group of disputed islands in the East China Sea, it was learned Sunday.

Diplomatic sources familiar with Sino-Japanese relations said Japan immediately rejected the Chinese demands, made through diplomatic channels, as "unacceptable" since the Senkaku Islands are administered by Japan.

It is unusual for China to call on the Japanese government to manage the operation of fishing boats in waters surrounding the inhabited islands, which the Chinese side calls Diaoyu.

The move appears aimed at weakening Japan's effective control over the islands and strengthening China's sovereignty claims.

The sources said China also demanded nullification of a resolution passed by the city assembly of Ishigaki on June 22 to change the name of the southern Japan area containing the Senkaku Islands from "Tonoshiro" to "Tonoshiro Senkaku," which Beijing sees as an attempt to cement Tokyo's claim.

Japan was said to have responded that the local assembly's decision cannot be changed as the area in question falls under its administrative authority.

The city in Okinawa Prefecture says that the renaming takes effect on Oct. 1, which is bound to cause controversy as that date coincides with the celebration of National Day of the People's Republic of China.

China reacted to the Ishigaki assembly's move by giving a set of names to seabed zones in the East China Sea including those related to the Senkaku Islands, causing Japan to protest.

Recently, activities of Chinese official vessels in waters around the disputed islands have been increasing, causing Japan to heighten its vigilance over what appears to be China's attempt to change the status quo.

The Chinese ships seem to be tracking the movements of Japanese fishing boats in the area.

On July 4, two China Coast Guard ships intruded into Japanese territorial waters for a record 39 hours and 23 minutes, the longest period of time since the islands were placed under Japanese state control in September 2012.

Six days later, Tokyo protested to Beijing over marine research activity by a Chinese ship in what Japan regards as its exclusive economic zone near Okinotori Island, the country's southernmost point of territory.

The Chinese Foreign Ministry Hua Chunying responded on Friday that "Japan's unilateral claim (to an EEZ around Okinotori) has no legal basis" as it does not constitute an island, just rocks.

Related coverage:

Japan now instantly scrambles jets against China's from Fujian

China seeks to boost clout, territory claims during pandemic: Japan

Japan protests China's seabed names related to disputed islands