Tokyo: China Coast Guard (CCG) vessels since March have been navigating in Japan's territorial waters around the Senkaku Islands in Ishigaki in Japan's Okinawa Prefecture. China Coast Guard vessels have been operating automatic identification system (AIS) equipment to announce their presence, The Japan Times reported citing Japan Coast Guard (JCG) sources.

The Japan Coast Guard is wary of such vessels as they believe that these aim to bolster China's arguments to the international community in order to gain control of the islands, Yomiuri Shimbun said in The Japan Times report.

According to sources related to the JCG, China Coast Guard vessels since March have been operating AIS devices in the territorial water and contiguous zone, The Japan Times reported. CCG vessels usually navigate in fleets of four. One such vessel with vessel number "1302" entered the contiguous zone on May 16.

The vessel appeared to be moving around Uotsuri Island, Kuba Island and entered Japan's territorial waters on May 20 and 21. As per the news report, the Chinese vessel in the territorial waters seemed to be tracking a Japanese fishing vessel.

According to the marine traffic website data, the vessel repeatedly changed direction on an irregular basis in the waters southeast of Minami-Kojima Island. Meanwhile, the Japanese Coast Guard patrol vessels which asked Chinese ships to leave the area did not operate their AIS equipment, The Japan Times reported.

Chinese government vessels have transmitted AIS information in the past. However, they stopped activating the system in 2018 when the China Coast Guard came under the command of the armed police force, The Japan Times reported.

An automatic identification system is a radio device that automatically shares and receives information on a vessel's position, course, speed and so on, The Japan Times reported.

According to the international convention for the safety of life at Sea, all passenger ships and other vessels engaged in international voyages need to carry this equipment, as per the news report. Radio transmissions are received by surrounding ships and are used to facilitate safe navigation in heavily trafficked sea regions.

Earlier in March, two Chinese vessels entered Japan's territorial water near the Senkaku Islands on Friday, pursuing two Japanese fishing boats in the East China Sea, Japan's NHK World reported. The two Chinese ships reportedly entered Friday in territorial waters off Taisho Island between 4:20 and 4:50 a.m. (local time).

The ships, along with two other Chinese ships, were previously cruising in the contiguous area just outside of Japan's territorial waters, the coast guard officials said. According to NHK World, the same Chinese ships also entered Japanese waters on Thursday.

The three Chinese ships entered the Uotsuri Island area's territorial waters on Thursday. It appears that they were also pursuing Japanese fishing vessels. For almost 17 hours, the ships stayed in Japanese waters, as per the news report. In order to protect the fishing boats and provide a warning to Chinese vessels to leave Japan's territorial waters right away, the Japanese coast guard sent out patrol boats.