China’s military sent 39 planes and three ships toward Taiwan in a 24-hour display of force directed at the island, Taiwan’s defense ministry said Thursday.

China’s military harassment of self-ruled Taiwan, which it claims is its own territory, has intensified in recent years, and the Communist Party’s People’s Liberation Army has sent planes or ships toward the island on a near-daily basis.

Between 6 a.m. Wednesday and 6 a.m. Thursday, 30 of the Chinese planes crossed the median of the Taiwan Strait, an unofficial boundary once tacitly accepted by both sides, according to Taiwan’s Ministry of National Defense.

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Those planes flew to the island’s southwest and then horizontally all the way to the southeastern side before doubling back, according to a diagram of the flight patterns provided by Taiwan. Among the planes were 21 J-16 fighter jets, 4 H-6 bombers and two early-warning aircraft.

Taiwan said it monitored the Chinese moves through its land-based missile systems, as well as on its own navy vessels.

China’s military held large military exercises in August in response to U.S. House speaker Nancy Pelosi’s visit to Taiwan. Beijing views visits from foreign governments to the island as de facto recognition of the island as independent and a challenge to China’s claim of sovereignty.

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In its largest military exercises aimed at Taiwan in decades, China sailed ships and flew aircraft regularly across the median of the strait and even fired missiles over Taiwan itself that ended up landing in Japan’s exclusive economic zone.