The Philippine Coast Guard has accused China of conducting illegal marine scientific research near the oil and gas-rich Reed bank within Manila's exclusive economic zone in the South China Sea, according to a statement on Thursday.
"We will continue to challenge any illegal activities that undermine our sovereignty and sovereign rights," PCG commandant Admiral Ronnie Gil Gavan said.
PCG aircraft spotted Chinese research vessel Xiang Yang Hong 33 near Iroquois Reef during a maritime patrol on May 6.
The PCG said the Chinese vessel was seen deploying a service boat toward the reef, confirming the ongoing "unauthorized" research operations.
One Chinese Coast Guard vessel and 13 Chinese maritime militia ships were also seen around the reef, it added.
It said the Chinese research vessel departed China on April 15 and conducted operations near Second Thomas Shoal, Sabina Shoal, Mischief Reef, and Jackson Atoll in recent weeks.
The China Coast Guard said a PCG aircraft "deliberately approached and harassed" the Chinese research vessel, and called the vessel's operations "a legitimate marine ecological survey".
The CCG accused the Philippines of distorting facts and warned it to "stop illegal harassment, smearing and inflammatory propaganda" in a statement on Thursday.
The PCG also monitored 28 Chinese maritime militia ships near Thitu island during the same maritime patrol.
The Philippines said China had no authorisation to conduct the marine research and called it a violation of Philippine sovereign rights as well as the United Nations Convention on the Law of the Sea.
Beijing's embassy in Manila said that Chinese research vessels conducting scientific missions in waters considered to be under China's jurisdiction were carrying out "normal activities" in accordance with international law.
(Reuters)