A Chinese military vessel locked its weapons-targeting radar on the Japanese warship Yuudachi, pictured, last week, Japanese officials say. (REUTERS)

A Chinese military vessel last week locked its weapons-targeting radar on a Japanese warship, Japan’s Ministry of Defense said Tuesday, marking a brief but dangerous escalation in the showdown over maritime territory between Asia’s two largest economies.

The Chinese ship eventually unlocked its radar without firing a shot, the ministry said, but the alleged incident underscores how the neighbors — wrangling over uninhabited islands in the East China Sea — are just one mistake away from potential armed conflict.

On Tuesday, Japan lodged a protest with the Chinese government over the incident, which it said took place near the contested islands that Japan calls Senkaku and China calls Diaoyu.

“Beaming of radar for firing is very abnormal, and it could have put us in a very grave situation if things went wrong,” Japan’s defense minister, Itsunori Onodera, told reporters, according to the Kyodo news agency. He added that in January, a Chinese ship targeted a Japanese helicopter in the same manner.

The two incidents mark the first times during the six-month maritime standoff that China has supposedly used such radar on Japanese ships or aircraft. According to Japan’s Asahi Shimbun newspaper, which cited Japanese Defense Ministry officials, the Chinese vessel and the Japan Maritime Self-Defense Force ship were less than two miles apart when the radar was used.

Island disputes in Asia

Although Tokyo and Beijing have long been at odds over the rocky chain of remote islands — the countries have competing narratives about decades- and centuries-old claims — tensions spiked in September when Japan bought three of the islands from a private landowner. Previously, Japan rented and controlled the islands, although China and Taiwan also staked claims.

Since the purchase, relations between China and Japan have hit their lowest point in decades. China has steadily increased its surveillance of the waters around the islands; incursions into Japanese territory, once rare, now occur almost daily.

More recently, China has been sending aircraft to the area, and on one occasion, China and Japan scrambled fighter jets in a game of cat-and-mouse. Both governments, hemmed in by nationalism, are limited in their ability to calm the situation, security analysts in Asia say.

China’s government describes its right to the islands as an “undeniable fact backed up by historical records,” and analysts say Beijing is pressing Tokyo to acknowledge that the territory is up for grabs. Japanese officials refuse to admit that a territorial dispute even exists; they say the islands are an “inherent” part of Japan, based on “historical facts,” according to a Foreign Ministry statement.

Japan’s new prime minister, Shinzo Abe, said several days ago that there is “no room for negotiations” over the islands, but he did raise the prospect of a meeting with Chinese leader Xi Jinping.