The Philippines said Sunday that more than 135 Chinese “maritime militia” ships were “swarming” a reef that it claims sovereignty over in the disputed South China Sea, with Manila calling the vessels’ ramped-up presence “alarming.”

The existence of the Chinese ships, ostensibly fishing boats, in the area of Whitsun Reef, which the Philippines calls Julian Felipe Reef, had grown since Nov. 13, when 111 of the vessels were detected, Philippine Coast Guard spokesman Jay Tarriela said in a statement.

Whitsun Reef in the Spratly Island chain, around 325 kilometers (200 miles) west of the Philippines’ Palawan Island, is also claimed by China and Vietnam. But it is more than 1,000 km from China’s nearest landmass, Hainan Island.