China's coast guard on Friday revealed it had entered restricted waters around an outlying Taiwanese island county in the Taiwan Strait, just off China's Fujian Province.

A formation of ships "carried out regular law enforcement inspections in waters near Kinmen in accordance with the law," the agency said without specifying the number of vessels. It added that the China Coast Guard would "resolutely safeguard" order within its jurisdiction as well as the lives and property of Chinese fishermen.

Accompanying the statement was a map with coordinates indicating the patrol sailed within what Taiwan considers to be restricted waters to the southeast of Kinmen's islands. The ships also briefly entered into a prohibited zone.

Taiwan stations troops on Kinmen, which at some points is just over a mile from Chinese shores. In the late 1950s it was at the center of clashes, including a failed amphibious invasion by China's People's Liberation Army, with intermittent shelling occurring until 1979.

This year, several high-profile episodes have stoked tensions between China and self-ruled Taiwan, which Beijing claims as its territory and has pledged to someday bring under its control—by force if necessary.

China has stepped up its coast guard patrols around Kinmen since February, when a speed boat capsized in nearby waters, drowning two Chinese fishermen. The boat had been fleeing Taiwan's coast guard after allegedly operating in Taiwanese waters.

Taiwan has empowered its coast guard to search and seize foreign-flagged vessels that enter prohibited waters or that remain in restricted waters after being issued two warnings to leave.

Beijing condemned its neighbor after the deaths of the men and just days later the Chinese coast guard boarded a Taiwanese tour boat sailing near Chinese waters, drawing a protest from Taipei.

Tzu-chieh Hung, associate research fellow at Taiwan think tank the Institute for National Defense and Security Research, previously told Newsweek he believes China is seeking to assert its sovereignty claims in the area. Deploying coast guard ships is one way to do this, without the military implications of a naval patrol, he said.

However, "given the close proximity of Kinmen and China, Taiwan has little room for concessions, especially if the Chinese coast guard were to regularly cross into prohibited waters near Kinmen while Taiwan adheres to standard operating procedures for necessary expulsions," Hung said.

Friday's incursion came as Taiwan prepares for the May 20 inauguration of President-elect Lai Ching-te of the ruling Democratic Progressive Party.

During his visit to China last week, U.S. Secretary of State Antony Blinken called for restraint from all sides in the weeks leading up to the inauguration ceremony.

Newsweek has reached out to Taiwan's Coast Guard Administration and China's foreign ministry with written requests for comment.