Japan-China relations are strained again, this time over a territorial dispute involving a group of uninhabited islets in a potentially oil-rich area of the East China Sea. On Wednesday, seven Chinese activists landed on one of the Senkaku Islands. Japanese police arrested them for violating the Immigration Control and Refugee Recognition Law. As a matter of course, the Japanese government lodged a protest with the Chinese government. Beijing, however, reiterated its position that the islands, known as Diaoyu in China, belong to the country, and demanded that Japan release the detainees "immediately and conditionally."

The Senkaku Islands, situated about 170 km northwest of Ishigaki Island, Okinawa Prefecture, is a part of Ishigaki City. In 1968, a U.N. geological survey raised the possibility that the seabed in the area might contain oil resources. After that, China, as well as Taiwan -- which calls the islets Tiaoyutai -- repeatedly claimed their territorial rights.

It is the first time that Japanese authorities have arrested Chinese nationals for illegally landing on a Senkaku islet. While the seven should be treated according to law, it is important that both countries deal with the incident calmly. Japan needs to prevent any provocative move, such as a landing excursion by a rightist group.