MANILA, Philippines (AP) — Chinese coast guard ships shadowed a group of Filipino activists and fishermen sailing on wooden boats towards toward a disputed shoal in the South China Sea, which Beijing has fiercely guarded from what it regards as intruders.

The Philippine coast guard deployed three patrol ships and a light plane to keep watch from a distance on the group of about 100 people, who set off from western Zambales province to assert Manila’s sovereignty over the Scarborough Shoal and surrounding waters. Dozens of journalists joined the three-day voyage.

The navy also dispatched a ship to help keep an eye on the participants.

The four wooden boats carrying the Filipinos were still far from the shoal when at least two Chinese coast guard ships began shadowing them at nightfall, said Emman Hizon, one of the organizers, adding that the participants remained in high spirits and would not turn back.