A Chinese warship collided with one of its own coast guard vessels while chasing Philippine boats earlier this week in the highly contested South China Sea, the latest incident that underscores growing volatility in one of the world’s most strategically vital waterways.

Two Chinese ships collided in the South China Sea Monday while one ship was chasing a Philippines Coast Guard vessel. Both sides claim the Scarborough Shoal.

China's coast guard said on Monday it took necessary measures to expel Philippine vessels from waters around Scarborough Shoal in the South China Sea. The coast guard said in a statement it monitored and intercepted the Philippine vessels after they ignored warnings,