Strongly worded letters all around as Vietnam enters Chinese/Philippine Sandy Cay dispute

Sandy Cay is close to Thitu Island, the largest and most strategically important of the nine features the Philippines occupies in the Spratly archipelago, where China, Malaysia, Taiwan and Vietnam also have a presence.

China claims more than 90 per cent of the potentially energy-rich South China Sea via a U-shaped "nine-dash line" on its maps that stretches into Southeast Asia and cuts into the exclusive economic zones of Brunei, Indonesia, Malaysia, Vietnam and the Philippines.

(Reporting by Phuong Nguyen; editing by Barbara Lewis)