TAIPEI (Taiwan News) — A Chinese missile frigate sailed past the coast of Hualien County just 10 nautical miles (18.5 km) outside Taiwan’s contiguous zone, reports said Tuesday (July 12).

A contiguous zone lies next to territorial waters and is designed to help authorities combat crime, so they can take action against criminals fleeing the territorial area. The outer limit of Taiwan’s contiguous zone lies 24 nautical miles from the baselines from which the breadth of the territorial sea is measured.

The People’s Liberation Army Navy (PLAN) missile frigate sailed from south to north around noon Sunday (July 10), passing just 35 nautical miles from the port of Hualien, CNA reported.

Defense officials said both the Navy and the Coast Guard kept a close watch on the movements of the Chinese warship during its passage close to Taiwan. According to military sources, the number of PLAN vessels appearing east of Taiwan declined in late June and early July for reasons unknown.

On Monday (July 11) afternoon though, a United States Navy destroyer sailed from north to south 45 nautical miles southeast of Taitung County’s Orchid Island, the military said.