Last 25 January, the Philippines suspended a scientific survey in the West Philippine Sea after two of its fisheries vessels faced "harassment" and aggressive behaviour from China's coast guard and navy.
Manila and Beijing have had a series of escalating confrontations in disputed waters of the South China Sea. China claims almost all the strategic waterway - through which US$ 3 trillion in commerce moves annually - overlapping sovereignty claims by the Philippines, Indonesia, Malaysia and Vietnam.
Two Philippine fisheries vessels, on their way to collect sand samples from Sandy Cay near Philippine-occupied Thitu island, encountered "aggressive manoeuvres" from three China Coast Guard ships, the Philippine Coast Guard said in a statement.
In its own statement, China Coast Guard said China has "indisputable sovereignty" over the Spratly Islands, including Sandy Cay - which China calls Tiexian Reef - and that it had intercepted two Philippine vessels and driven them away in accordance with law.
China Coast Guard said the Philippine vessels had entered waters near Tiexian Reef without permission and attempted to "illegally" land on the reef to collect sand samples.
China deployed four small boats from its larger coast guard vessels to "harass" two rigid hull inflatable boats deployed by the fisheries bureau to transport personnel to Sandy Cay, said the Philippine Coast Guard, which supported the scientific mission.
A Chinese navy helicopter also hovered at an "unsafe altitude" over the water craft, it said.
Survey operations were suspended "as a result of this continuous harassment and the disregard for safety exhibited by the Chinese maritime forces," the Philippine Coast Guard said.
Manila and Beijing agreed during a round of talks on 16 January to seek common ground and find ways to cooperate despite their disagreements over territorial claims in the South China Sea.
An international arbitration tribunal ruled in 2016 that China's claims, based on its historic maps, have no basis under international law, a decision Beijing does not recognise.