Tokyo has said that a Chinese naval submarine spotted in waters off flashpoint islands in the East China Sea was one of its new nuclear-powered attack vessels, AFP reported on Monday. The statement comes on the same day that China announced that three of its “coastguard vessels conducted a patrol in territorial waters off the Diaoyu Islands,” Beijing’s name for contested isles called Senkaku in Japan. Japanese Defense Minister Itsunori Onodera said on Monday that the submarine has been determined to be “China’s Shang-Class nuclear-powered attack submarine,” which he said can be equipped with long-range cruise missiles. “The submarine’s underwater passing through our country’s contiguous waters is an act that unilaterally increases tension,” he added. Beijing has not confirmed whether it had sent a submarine.