Japan summoned China's ambassador to protest an "incursion" of Chinese surveillance ships near disputed islands on Tuesday, and Japan's new Prime Minister Shinzo Abe ordered, according to Reuters, more surveillance around those same islands.
"I want you to respond firmly," Kyodo news agency quoted Abe telling Defense Minister Itsunori Onodera.
Both states claim the cluster islands in the South China Sea, known as Diaoyu to the Chinese, and Senkaku to the Japanese. Taiwan also claims the islands.
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China responded with a statement.
"Japan has continued to ignore our warnings that their vessels and aircraft have infringed our sovereignty," said Sun Shuxian, Communist Party chief of China's marine surveillance corps, adding, "This behavior may result in the further escalation of the situation at sea and has prompted China to pay great attention and vigilance."
The International Business Times points out Japan's maneuvers come during a military strategy review, which may result in an increased military budget - the first in a decade.