Taiwan said on Wednesday it would exercise its right to self-defence and counter-attack if Chinese armed forces entered its territory, as Beijing increased military activities near the democratically governed island.
Beijing, which claims Taiwan as its own against the strong objections of the Taipei government, has held military exercises around the island this month in reaction to a visit to Taipei by US House of Representatives Speaker Nancy Pelosi.
Taiwanese defence officials said China's "high intensity" military patrols near Taiwan continued and Beijing's intention to make the Taiwan Strait separating the two sides its "inner sea" would become the main source of instability in the region.
"For aircraft and ships that entered our sea and air territory of 12 nautical miles, the national army will exercise right to self-defence and counter-attack without exception," Lin Wen-Huang, Taiwan's deputy chief of the general staff for operations and planning, told reporters.
Taiwan has complained of Chinese drones repeatedly flying close to its small groups of islands near China's coast.
The military would exercise the same right to counter-attack Chinese drones that did not heed warnings to leave Taiwanese territory after posing threats, Lin added.
Taiwan fired warning shots at a Chinese drone for the first time on Tuesday shortly after President Tsai Ing-wen ordered the military to take "strong countermeasures" against what she termed Chinese provocations.
Taiwan's army said its forces again fired warning shots and flares on Wednesday at drones buzzing islets in its Kinmen chain, which are situated just offshore from the Chinese cities of Xiamen and Quanzhou.
The drones then flew back to Xiamen, it added.
Chinese Foreign Ministry spokesperson Zhao Lijian, in a regular press briefing, reiterated Beijing's position that Taiwan belonged to China.
"Firstly I need to tell you, Taiwan is a province of China, it has no so-called defence ministry. The Taiwan authorities are playing up their nervousness, this is meaningless," he said.
Earlier in the week, the ministry dismissed complaints from Taiwan about drone harassment as "not worth fussing about".
In the same briefing, Ma Cheng-Kun, a director at the National Defence University military academy, said China might further move to reject passage of foreign naval ships through the strait without its permission.
"After the new military normal status has been consolidated, then the risk of collision will increase if foreign naval ships insist on the rights of navigation and freedom," he said.
White House national security spokesman John Kirby told reporters that China continued to try to "permanently alter" the status quo around Taiwan, and that the US wouldn't accept it.
"The concerns expressed by leaders in Taiwan are understandable given the aggressive, assertive, coercive, and quite frankly, unnecessary, activities that the PRC continues to conduct from a military perspective in and around the Strait," Kirby said, referring to the People's Republic of China.
US warships and those from allied nations such as Britain and Canada have routinely sailed through the Taiwan Strait in recent years, including two US Navy warships last week.
Taiwan's armed forces are well-equipped but dwarfed by China's. Tsai is overseeing a modernisation programme and has made increasing defence spending a priority.
China has not ruled out using force to bring the island under its control. Taipei rejects Beijing's sovereignty claims, saying that the People's Republic of China has never ruled the island and that only Taiwan's people can decide their future.