TAIPEI (Taiwan News) — The defense ministry reported nine Chinese military aircraft and five vessels around Taiwan between 6 a.m. on Friday and Saturday.

Six of the aircraft crossed over the median line of the Taiwan Strait and entered the country’s northern, southwestern, and southeastern air defense identification zones, or ADIZ. In response, Taiwan sent aircraft and naval ships and deployed coastal-based missile systems to monitor Chinese activity.

So far this month, Taiwan has tracked 331 Chinese military aircraft and 220 ships. Since September 2020, China has increased its use of gray zone tactics by incrementally increasing the number of military aircraft and naval vessels operating around Taiwan.

Gray zone tactics are “an effort or series of efforts beyond steady-state deterrence and assurance that attempts to achieve one’s security objectives without resort to direct and sizable use of force.”