HANOI - Vietnam on Thursday (May 18) criticised recent conduct by a Chinese research ship and the Philippine coast guard in the South China Sea, accusing its neighbours of separate actions that were violating its sovereign rights.

Tensions are high in contested parts of the South China Sea, one of the world's most important trade routes and a conduit for more than US$3 trillion (S$4 trillion) of annual ship-borne commerce.

Chinese and Vietnamese vessels confronted each other in recent days on multiple occasions as a Chinese research ship moved within Hanoi's Exclusive Economic Zone (EEZ), which experts said was likely a survey. Such a survey would usually be considered hostile if conducted without notification.

Asked for comment, Vietnamese Foreign Ministry spokesperson Pham Thu Hang told a press conference those vessels were "violating the sovereign rights and jurisdictions of Vietnam", which was taking "appropriate measures" to defend its rights.

China has said that scientific research is a normal activity in areas under Chinese jurisdiction.

China claims almost the entire South China Sea as its territory, based on what it says are old maps, including waters that lie within the EEZ of Vietnam and four other Southeast Asian countries.

The Philippines was also rebuked for placing navigational buoys in five areas of its EEZ to assert sovereignty over the hotly disputed Spratly islands, to parts of which Vietnam also lays claim.

Asked about the Philippines' move, Hang said: "Vietnam strongly opposes all acts violating Vietnam's sovereign rights."

Philippine Foreign Ministry spokesperson Teresita Daza said Manila's coast guard's installation of buoys was consistent with the country's rights as a coastal state under the UN Convention on the Law of the Sea.

"They are meant to improve safety of navigation in our waters and should be of no cause for concern," Daza told Reuters in a phone message.

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Source: Reuters