Keeping up pressure, China sends warships and fighter jets near Taiwan during Yellen's Beijing visit

Taiwan's Defense Ministry says China has sent 13 aircraft and 6 vessels to airspace and waters around Taiwan as of early Saturday

China’s People’s Liberation Army sent 13 aircraft and 6 vessels into airspace and waters around Taiwan over the past 24 hours as of early Saturday, overlapping with United States Treasury Secretary Janet Yellen’s visit to Beijing aimed at mending strained relations.

Taiwan's Defense Ministry said it is monitoring the situation from the air and sea, and land-based missile systems were prepared to respond. It said four Chinese aircraft — two SU-30 fighters, one BZK-005 reconnaissance plane and one Y-8 anti-submarine warfare plane — crossed the median line in the Taiwan Strait that serves as a de-facto border between the sides, and had entered Taiwan's southwestern air defense identification zone.

China claims Taiwan as its own territory to be annexed by force if necessary and sends air and naval missions on virtually a daily basis in an attempt to wear down the island’s defense capabilities and intimidate its 23 million people, who thus far seem largely unfazed by such moves.

U.S. support for the self-governing island republic that split from mainland China amid civil war in 1949 remains a major irritant in relations with Beijing.

Shortly before Yellen’s arrival, Chinese President Xi Jinping visited the headquarters of the People’s Liberation Army’s Eastern Theater on Thursday. Its area of operations directly faces the island across the Taiwan Strait.

Addressing commanders at the Jiangsu province headquarters, Xi “stressed efforts to … break new ground for theater command development and war preparedness,” state media reported.

He called for “enhancing the planning of war and combat … and stepping up training under real combat conditions to raise the forces’ capabilities to fight and win,” the reports said.

The PLA, the world's largest standing armed force, serves as the military wing of the Communist Party and is overseen by a committee headed by Xi.

Beijing also objects vigorously to United States military support for Taiwan, and lashed out Wednesday at an upcoming $440 million sale of cannon shells and other equipment, accusing the U.S. of turning Taiwan into a powder keg.

Yellen is not expected to meet with Xi during her visit.