The U.S. Marine Corps' new amphibious assault combat vehicles (ACVs) made their regional debut during the exercise. In another first, a Philippine navy frigate fired anti-ship cruise missiles against a decommissioned warship.

China's military said it closely monitored and "drove away" USS Halsey that entered the territorial waters of Paracel Islands in the South China Sea on May 10, the Southern Theater Command of the People's Liberation Army said in a statement on Friday.

An escalating diplomatic row and recent maritime run-ins between China and the Philippines have made the highly strategic South China Sea a flashpoint. WHAT ARE THE FLASHPOINTS? Central to recent standoffs between the Philippines and China are two hotly contested features located inside Manila's 200-nautical mile exclusive economic zone,