TOKYO - The unprecedented entry of a Chinese advanced stealth nuclear submarine into waters near islets contested by Japan and China in the East China Sea has jeopardised tentative moves to improve bilateral ties.
Japanese Defence Minister Itsunori Onodera on Monday (Jan 15) slammed the Chinese action last Thursday as one that "unilaterally raises tensions". Beijing, however, said that it was merely tracking and monitoring two Japanese naval ships passing through the area.
The Chinese submarine has been identified as a new Shang-class vessel that is 110m long and has a displacement of 6,100 tons. It can be equipped with torpedoes and cruise missiles longer in range than on conventional submarines.
In a separate incident on Monday, three China Coast Guard patrol vessels entered the territorial waters around the islets known as Senkaku in Japan and Diaoyu in China. It was the second such incident this year with the first occuring last Sunday (Jan 7).
Tokyo has lodged protests against these "incursions", prompting Beijing to retort that it does not accept these representations as it considers the islets as Chinese territory.
"We urge Japan to stop stirring up trouble on the Diaoyu islands issue," Chinese Foreign Ministry spokesman Lu Kang said in Beijing on Monday, in response to questions posed by Japanese public broadcaster NHK.
Earlier at a news conference in Tokyo on Monday, Japan's Chief Cabinet Secretary Yoshihide Suga had described the Senkaku islands as "Japan's inherent territory legally and historically". He also said the spate of incidents recently was "extremely regrettable".
Last week, Mr Suga reaffirmed that Japan would "resolutely defend its land, territorial waters and airspace", while handling the situation "firmly and calmly".
Waters surrounding the uninhabited islets, which are administered by Japan, are said to be rich in oil and natural resources. The islets have, time and again, caused tensions between China and Japan and the latest incidents have come as ties were improving. Chinese President Xi Jinping and Japanese Prime Minister Shinzo Abe vowed a "fresh start" to relations in rare bilateral talks last November.
Last Thursday's incident marked the first time since June 2016 that a Chinese military vessel had entered the so-called "contiguous zone" around the disputed islets. It also marked the first time that a nuclear submarine entered the area.
Mr Onodera, speaking to reporters on Monday, said: "Such nuclear-powered submarines are difficult to detect because they can remain far beneath the surface for extended lengths of time. We'll keep our guard up to respond swiftly if a similar incident happens."
Mr Suga, for his part, stressed on Monday the urgency to step up bilateral efforts to realise an air and maritime communication mechanism to avoid an accidental conflict in and over the East China Sea.
A nation's "territorial waters" refer to an area extending out 12 nautical miles from the coast, while the "contiguous zone" refers to the band of water in an area between 12 and 24 nautical miles from land.
The submarine's movement through the contiguous zone does not contravene international law. Beijing's Ministry of National Defence had voiced "strong discontent with Japanese efforts to sensationalise a legitimate action by the Chinese navy".
Nonetheless, Japan's conservative daily Yomiuri Shimbun slammed the Chinese action as one that, while legal, "needlessly raises tensions" and said it was "unacceptable from the viewpoint of security". It added that China's unilateral claims over the islands were "irrelevant".
Emeritus professor Shinya Murase of Tokyo's Sophia University observed that Chinese ships had periodically entered Japanese waters as a means to "demonstrate its position that the islets belong to China".
"Intrusion into territorial waters by the coast guard vessels is clearly a violation of the state's sovereignty," added Dr Murase, who is a visiting professor at China's Peking University and is a member of the United Nations International Law Commission.
He said that China ought to resolve the issue by peaceful means, such as taking its claims up at the International Court of Justice.
The University of Tokyo's Dr Shin Kawashima, who studies Sino-Japan ties, said the entry of a nuclear submarine into waters near the disputed islands marked a "new phase in Chinese escalation".
He added: "China is sending a message to Japan that while on the one hand, it is willing to improve bilateral ties, on the other it will not loosen its stance on territorial and security issues in the East China Sea."