Taiwan has scrambled jets and navy ships as two mainland warships sailed through the Taiwan Strait, in the latest sign of heightened tensions between Beijing and the self-ruled island. The PLA Navy warships – a Type 052C destroyer and a Type 054A frigate – sailed southward off the island’s east coast early on Friday, Taiwan’s defence ministry said. “They were moving in open sea close to Taiwan’s territorial waters before passing through the Bashi Channel, south of Taiwan,” the ministry said in a statement on Saturday. It said the mainland vessels, which were sailing southwest to the South China Sea, appeared to be on a long-distance training mission. “We immediately scrambled jets and navy ships to monitor the movement of the vessels in line with our regulations,” the ministry said. Taiwan’s critical battle to keep its diplomatic allies from switching sides Taiwanese newspaper United Daily News reported on Friday that the Jinan destroyer and Huanggang frigate had sailed into the Taiwan Strait last week, within the island’s air defence identification zone, and at one stage they were just 60 nautical miles from the islet of Xiaoliuqiu near Kaohsiung. It said the vessels stayed near Taiwan for more than a week before sailing towards the South China Sea on Friday. The People’s Liberation Army has stepped up air force and naval training missions either close to Taiwan or surrounding the island in the past two years since Tsai Ing-wen became president. Cross-strait relations turned sour after Tsai, of the independence-leaning Democratic Progressive Party, took office in 2016 and refused to accept the one-China principle. US unveils new ‘embassy’ in Taiwan amid strained ties with China Beijing considers Taiwan a breakaway province subject to eventual reunification, by force if necessary. It insists that the one-China principle is the foundation for cross-strait relations and has suspended official exchanges with the island as it tries to force Tsai to accept the principle. On Friday, Tsai told scholars from a Washington-based think tank that Beijing’s “bullying” was to blame for escalating cross-strait tensions and would undermine stability in the region. She vowed to work more closely with the United States to try to counter pressure from the mainland. Washington has committed to support the island, even though they have not had official ties since the US switched diplomatic recognition from Taipei to Beijing in 1979. The US is also considering sending a warship through the Taiwan Strait in what would be seen by Taipei as a sign of support following mainland Chinese military exercises around the island, according to a Reuters report early this month quoting unnamed US officials. The mainland’s foreign ministry responded by urging Washington to act prudently. “We have repeatedly emphasised that the Taiwan issue is the most important and sensitive core issue in the China-US relationship,” ministry spokeswoman Hua Chunying said in Beijing after the report came out.