A Chinese coast guard ship and an accompanying vessel rammed a Philippine coast guard ship and a military-run supply boat Sunday off a contested shoal, Philippine officials said, in an encounter that heightened fears of an armed conflict in the disputed South China Sea.

A top Philippine security official told The Associated Press there were no injuries among the Filipino crew members and an assessment of the damage to both vessels was underway.

The official said that the two incidents near Second Thomas Shoal, where China has repeatedly tried to isolate a Philippine marine outpost, could have been worse if the vessels were not able to maneuver rapidly away from the Chinese ships. The official spoke on condition of anonymity due to a lack of authority to publicly discuss the matter.