'Air defense zone' feud heats up between China and Japan

Japanese Prime Minister Shinzo Abe answers a question during the Upper House's audit committee session at the National Diet in Tokyo on November 25, 2013. China's declaration of an air defence identification zone that includes disputed islands is 'profoundly dangerous', Japan's prime minister said.

China hit back Monday at what it called “irresponsible remarks” over its recently announced air defense zone over the East China Sea. The zone would include waters and islands whose ownership is claimed by both China and Japan.

Japanese Prime Minister Shinzo Abe called the newly declared zone dangerous and unenforceable.

"The measures by the Chinese side have no validity whatsoever for Japan, and we demand China revoke any measures that could infringe upon the freedom of flight in international airspace," Abe said Monday.

"It escalates the situation and could lead to an unexpected occurrence of accidents in the airspace. It is an extremely dangerous measure and our government has strongly expressed its concerns about it," he said, while speaking to parliament.

The zone, unveiled by Beijing on Saturday, would require airlines to inform Chinese authorities of their flight plans before entering the airspace above the East China Sea.

"If an aircraft doesn’t supply its flight plan, China’s armed forces will adopt emergency defensive measures in response," Chinese state news agency Xinhua reported.

US Secretary of State John Kerry and Defense Secretary Chuck Hagel both responded to the new policy Saturday, saying the United States was “deeply concerned.”

China's Foreign Ministry said it complained to the United States for its "irresponsible remarks" Monday, while the Chinese Defense Ministry called Japan's objections "absolutely groundless and unacceptable."

The war of words centers around the disputed territory of the Senkaku islands — as they're known in Japan — or Diaoyu — as they're known in China. As The Wall Street Journal noted, the islands "represent important sacred symbols of sovereignty for both Japanese and Chinese." Japan currently controls the islands.

The Chinese air force conducted its first air patrol shortly after the zone was announced, according to Xinhua.

While the United States has no stance on the ownership of the islands, it recognizes Japan's administrative control of them and would be bound by treaty to defend its ally in case of conflict.

More from GlobalPost: What Japan and China stand to gain, and lose, in Senkaku