No fewer than 260 Chinese naval vessels strayed into Korean-controlled waters last year. The most frequent incursions were into Korea's exclusive economic zone west and south of the country, but there were also intrusions into the East Sea. The EEZ is the area in a certain distance of a country's coastline where a country claims exclusive rights for fishing, drilling and other economic activities. Over the last five years, China has boosted its naval force by 25,000 to 260,000 sailors and added one more aircraft carrier and 16 destroyers. The increasing incursions are seen as a show of force in the region.According to data from the Defense Ministry, around 260 Chinese naval vessels conducted operations in Korean-controlled waters last year. Some 160 strayed into the South Sea, 80 into the West Sea and 20 into the East Sea.But none violated territorial waters.The most recent incursion was a Chinese naval intelligence ship that appeared in the East Sea on Sept. 23, when the U.S. nuclear-powered aircraft carrier Ronald Reagan docked in Busan. Japan's Joint Staff Office said Monday that the vessel was spotted 100 km southwest of Tsushima Island on Sept. 23, heading to the East Sea after crossing the Tsushima Strait.