The Philippine Coast Guard has accused its Chinese counterpart of firing water cannon at its vessels and blocking them in the disputed South China Sea, APA reports.
It said this happened when its ship was escorting boats carrying supplies for Filipino soldiers stationed on one of the contested Spratly Islands.
The US condemned Beijing's "dangerous actions", also blaming Chinese "maritime militia" for the incident.
China has not publicly commented on the reported incident.
Beijing claims almost the entire South China Sea, including the Spratlys, which is also claimed in part by the Philippines.