China’s Coast Guard said Friday it had taken unspecified “control measures” against two Philippine vessels that it accused of making “provocative collisions” near Second Thomas Shoal, a disputed reef known in China as Ren’ai Jiao. Spokesman Gan Yu claimed the boats had launched from the grounded Philippine warship BRP Sierra Madre and approached Chinese ships in an “unprofessional and dangerous manner.” Beijing demanded Manila “immediately cease all infringement, provocations and false accusations,” adding that it would continue law-enforcement patrols in the area. The warning followed a report from the Philippine military that Chinese coast-guard and militia vessels around the shoal had increased in number earlier in the week. Second Thomas Shoal, part of the Spratly Islands, has been occupied by Philippine Marines since 1999 and sits within the Philippines’ exclusive economic zone, according to a 2016 international tribunal ruling that China rejects. Beijing’s latest stance was reinforced by three papers released a day earlier by the Xinhua Institute, which argued that China has “historical and legal” sovereignty over much of the South China Sea. The studies accused the United States of spreading “lies” about Chinese intentions and alleged that unspecified external forces were stoking regional tensions. The confrontation underscores escalating frictions in the South China Sea, where China, the Philippines, Vietnam, Malaysia, Brunei and Taiwan hold overlapping claims. Manila has stepped up patrols and deepened security cooperation with the United States, moves that Beijing says amount to outside interference in the disputed waters.