A Chinese vessel and a Philippine supply ship collided near the disputed Spratly Islands in the South China Sea on Monday, according to China’s coast guard.

The coast guard reported that the Philippine supply ship entered waters near the Second Thomas Shoal, a submerged reef in the Spratly Islands that is claimed by multiple nations.

In a statement on the social media platform WeChat, the Chinese coast guard stated that the Philippine supply ship “ignored China’s repeated solemn warnings and dangerously approached a Chinese vessel in normal navigation in an unprofessional manner, resulting in a collision.” The statement added, “The Philippines is entirely responsible for this.”

No immediate comment was available from the Philippine government.

The Philippines asserts that the shoal, located less than 200 nautical miles (370 kilometers) from its coast, lies within its internationally recognized exclusive economic zone. The country often references a 2016 international arbitration ruling that invalidated China’s extensive claims in the South China Sea based on historical grounds.

Several incidents have occurred in recent months near the shoal, where the Philippines maintains a post aboard the BRP Sierra Madre ship.

These territorial disputes have strained relations and raised fears that the conflict could escalate, potentially drawing China and the United States, a longtime treaty ally of the Philippines, into a military confrontation. While Washington has no territorial claims in the busy seaway, it has warned that it is obligated to defend the Philippines if Filipino forces, ships, or aircraft come under armed attack in the South China Sea.

Besides China and the Philippines, Vietnam, Malaysia, Brunei, and Taiwan are also involved in the long-standing territorial disputes, which are considered a flashpoint in Asia and a delicate fault line in the enduring U.S.-China rivalry in the region.