Taiwan's defense ministry said a pair of Chinese J-11 jet fighters crossed the line at around 11 a.m. Sunday and entered the island's southwestern airspace. It said Taiwan scrambled jets to warn off the Chinese planes, which came within about 185 kilometers (115 miles) of Taiwan.
"Yesterday, Chinese military aircraft provoked us by violating the tacit agreement by crossing the median line of the Taiwan Strait. They backed to the west side of the median line after warnings by our Air Force," Taiwanese President Tsai Ing-wen said in remarks at a military awards ceremony.
Foreign Ministry Joseph Wu told reporters at the legislature that the line crossing was an intentional act, calling it a provocative and dangerous. He said Taiwan had informed "regional partners" about the incident.
About 160 kilometers (100 miles) wide at its narrowest, the Taiwan Strait opens at its southern end into the South China Sea, where Taiwan and China share overlapping territorial claims. Since the sides split amid civil war in 1949, China has claimed Taiwan as its own territory to be absorbed by force if necessary.
Tsai, who Beijing despises for her pro-independence views, has sought to bolster Taiwan's air power with the purchase of latest-model F-16V fighters from the U.S., Taiwan's chief source of defensive weapons.