MANILA, Philippines (AP) — The Philippines has protested actions by the Chinese coast guard that prevented delivery of supplies to a small group of Filipino soldiers guarding a shoal in a disputed area in the South China Sea.

The Department of Foreign Affairs said in a statement Tuesday that Chinese ships prevented Filipino civilian vessels hired by the Philippine navy Sunday from reaching Second Thomas Shoal, which is called Ayungin Shoal by Manila and Ren’ai Reef by the Chinese.

China’s charge d’affaires was summoned and handed the protest note. Less than a month ago, Manila also protested a Chinese water cannon attack on Filipino fishermen near another disputed shoal.

The Filipino troops are stationed on a decrepit military hospital ship that ran aground in 1999 on the shallow coral outcrop of the shoal.