Photo: Screenshot of Japanese media Abema News

A Chinese Navy survey ship sailed through the Tokara Strait, a strait for free international navigation, rather than Japan's territorial waters, the Global Times learned on Monday after Japan had accused the Chinese vessel of entering its territorial waters.

Japan's Ministry of Defense said on Monday that "it was confirmed that a Chinese Navy Shupang-class survey ship sailed through Japan's territorial waters." Japan's Defense Ministry spotted the survey ship's navigation route, saying Japan's Maritime Self-Defense Forces were on high alert and were monitoring the vessel.

According to Japan's description, the Chinese ship's navigation route was through the Tokara Strait, where all countries' vessels have the right of transit passage with no prior notice or approval required, an expert told the Global Times on Monday.

Kyodo news reported that Japan has expressed concerns about the so-called "intrusion" to the Chinese side via diplomatic channels. Experts said that claiming Chinese ships have entered its territorial waters has become Japan's regular way to hype the "China threat theory."

"We can see both the Japanese government and media have deliberately not mentioned the fact that the Chinese vessel complied with the passage required by international law," Lian Degui, director of the Department of Japanese Studies at Shanghai International Studies University, told the Global Times.

Song Zhongping, a Chinese military expert and TV commentator, told the Global Times on Monday that many straits near Japan are international straits where foreign warships can freely pass and it is a common international practice for the Chinese Navy to carry out scientific research in the international waterways.

Song said that Japan should abandon the double standard on Chinese vessels as vessels of the US and Japan have regularly approached the Chinese periphery and launched reconnaissance activities.

Experts said that China's regular scientific research behavior does not threaten Japan, and urged Japan not to use it as an excuse for revising its national security documents.