Why is a Chinese research ship the latest flashpoint with Philippines in South China Sea?

Beijing and Manila have traded accusations over a Chinese research vessel near a disputed South China Sea reef, with each side warning of further countermeasures in a sign of lingering tensions between the rival claimants. In a statement issued on Thursday night, the China Coast Guard (CCG) said a Philippine Coast Guard Islander aircraft had “deliberately approached and harassed” China’s Xiang Yan