China's coast guard said the Philippines on Friday sent a civilian vessel to deliver provisions to its warship "illegally grounded" at Second Thomas Shoal, a disputed atoll in the South China Sea. The coast guard "questioned" and "monitored" the Philippine vessel throughout its supply mission,

Tensions between Beijing and Manila have intensified in recent months concerning the South China Sea, a region spanning 3.5 million square kilometers (1.35 million square miles) through which an estimated $11.3 billion in global trade passes annually, according to the Center for Strategic and International Studies.

Two Philippine ships had to call off their scientific probe after Chinese vessels and a helicopter intercepted them near the Spratly archipelago, according to the Philippines' coast guard.