The swarming of Chinese fishing vessels in several locations in the country's exclusive economic zone in the West Philippines Sea has alarmed the Western Command of the Armed Forces of the Philippines.

AFP's WesCom said Thursday that at least 30 Chinese fishing vessels were spotted  in the WPS by its aerial patrols from 6 to 7 September.

A total of 23 vessels were monitored at Rozul or Iroquois Reef, five  boats were spotted at Escoda or Sabina Shoal, while two were seen at Baragatan or Nares Bank.

The Philippine Navy, likewise, spotted 33 Chinese fishing vessels at Rozul Reef during a routine air patrol on 24 August, which was followed by reports of massive coral harvesting.

The WesCom said the same patrols also monitored swarming activities on Escoda Shoal. The area serves as a "marker for the approach to Ayungin or Second Thomas Shoal" where the "unauthorized Chinese shadowing of Philippine watercraft typically occurs."

It stressed that Rozul Reef is located within the Philippines' EEZ and continental shelf, "making this intrusion a violation of Philippine sovereign rights and jurisdiction."

Meanwhile, 48 Chinese fishing boats were seen last 30 June at Iroquois Reef, located south of the oil and gas-rich Recto Bank, which also lies within the country's EEZ.

"The increased presence of Chinese fishing vessels raises concerns of the potential implications for the Philippines' maritime security, fisheries conservation, territorial integrity, and preservation of the marine environment," WesCom said.