Japan lodged a protest with its neighbor after the submarine and the Chinese vessel approached what Tokyo considers as its territorial waters around the Japanese-administered Senkaku Islands, Japan's Defense Ministry said. The Japanese Ministry of Defense did not immediately clarify if the Chinese frigate, which was a Type 054A Jiangkai-II-class frigate, belonged to the People's Liberation Army-Navy (PLAN) or the China Coast Guard, which uses the Type 054A as well. "We are deeply concerned", Defence Minister Itsunori Onodera told reporters.
Sugiyama expressed "great concern" over the provocations and strongly urged China not to hinder efforts to improve the countries' relationship. Just $5 a month.
Japan and China have renewed their war of words over a group of disputed islets after Japan reported spotting a Chinese warship and an unidentified submarine in the East China Sea. Officials from both sides met in Shanghai for two days and made a decision to implement the hotline.
In 2004, the government ordered an SDF maritime security operation after a Chinese nuclear submarine intruded into Japanese waters around the Saki-shima island chain, southern Japan.
Global law requires submarines to surface and hoist the national flag when navigating through territorial waters of other nations, but not in contiguous zones. The Chinese ship did not enter Japanese territorial waters. It then re-entered the contiguous zone around Taisho Island, which is part of the Senkakus, before leaving that afternoon.
Japan protested to China on Friday after a foreign submarine in waters near disputed islands in the East China Sea was confirmed to be Chinese, calling it a unilateral action and a "serious escalation" that raised bilateral tensions.
China's defense ministry said that a Chinese missile frigate had responded to two Japanese ships entering its claimed waters but that the ships had now left.
A foreign submarine was also detected in the same area on Wednesday as well as on Thursday, according to Japan's Defense Ministry. But the submarine is believed to be from China as well, informed sources said.