China's announcement it would bring a flight path for civilian aircraft closer to the median line in the Taiwan Strait, which has effectively served as a "borderline" between the two sides, triggered protests from the self-ruled island on Wednesday.

The Civil Aviation Administration of China said Tuesday it was canceling an "offset measure" for the southbound operation of the M503 flight route, which was set by the mainland just west of the median line in 2015.

Taiwan Premier Chen Chien-jen on Wednesday condemned Beijing's "unilateral" change to the path, saying it would affect flight safety. Taipei "hopes that the Chinese government can stop these inappropriate actions," he said.

As Taipei had protested that the original M503 path was too close to the median line, the two sides later agreed that Beijing would operate the route by moving it 6 nautical miles (about 11 kilometers) westward toward the mainland.

Chen Binhua, a spokesman for the State Council Taiwan Affairs Office, speaks at a press conference in Beijing on Jan. 31, 2024. (CNS/Kyodo)

With the cancelation of the westward route, civil aircraft will fly along the original path, which is just 7.8 km away from the median line at the closest point.

China, which views the self-ruled democratic island as part of its own territory, has in recent years ignored the median line in the Taiwan Strait, a boundary both sides had tacitly respected for decades, by having its military vessels and warplanes cross the line.

Taiwan's Defense Ministry warned Wednesday that China's "arbitrary actions" of changing the flight path could escalate cross-strait tensions.

The island's Mainland Affairs Council called Beijing's move a deliberate attempt to use civil aviation as cover for political and possibly military intentions, aimed at changing the status quo of the Taiwan Strait.

Chen Binhua, a spokesman for the State Council Taiwan Affairs Office, said at a press conference on Wednesday that adjusting the M503 flight route is a "routine task" of the mainland civil aviation authorities for alleviating airspace congestion and that there was no need for Beijing to negotiate the matter with Taipei.

He also said Taiwan is an inalienable part of Chinese territory and that the median line does not exist. Communist-led China and Taiwan have been governed separately since they split in 1949 as the result of a civil war.

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