Chinese and Philippine coast guard vessels collided in the disputed South China Sea and four Filipino crew members were injured Tuesday in high-seas confrontations as Southeast Asian leaders gathered for an Asian summit where alarm over Beijing’s aggression at sea was expected to be raised.

The Chinese coast guard ships and accompanying vessels blocked the Philippine coast guard and supply vessels off the disputed Second Thomas Shoal and executed dangerous maneuvers that caused two minor collisions between the Chinese ships and two of the Philippine vessels, Philippine officials said.