Vietnam said it would welcome foreign involvement to keep the peace, in an apparent reference to the United States, which last year angered China by offering to mediate in the South China Sea disputes and calling them a matter of its own national interest

Vietnam fired artillery rounds off its central coast on Monday in naval drills announced during a maritime spat with Beijing, as conflicts heat up between China and its neighbours over the potentially oil—rich South China Sea.

Vietnam accuses Chinese boats of disrupting oil and gas exploration in its waters, echoing a similar dispute that flared last week with the Philippines concerning Beijing’s reported moves to assert its sovereignty over disputed areas in recent months.

Vietnam said it would welcome foreign involvement to keep the peace, in an apparent reference to the United States, which last year angered China by offering to mediate in the South China Sea disputes and calling them a matter of its own national interest.

The Vietnamese live—fire drills began at the uninhabited island of Hon Ong, some 25 miles (40 kilometers) off the coast, said a naval officer based in central Quang Nam province. He declined to give his name because he was not authorized to speak to the press.

Despite the disagreement with China, he said the drills were routine annual exercises involving artillery and other weapons. He said no missiles would be fired, and declined to say how many troops or vessels were be involved. A second manoeuvre lasting five hours was scheduled for the evening.

Wang Hanling, a Chinese maritime expert at the Chinese Academy of Social Sciences who is currently a visiting research fellow at the East Asian Institute in Singapore, criticized the drills, saying Beijing has consistently sought to settle issues in the South China Sea peacefully.

“Any action leading to the escalation of the situation won’t help, especially military exercises either by Vietnam or other countries, are not helpful,” Mr. Wang said.

Vietnam maintains Chinese boats cut a cable attached to an oil exploration vessel conducting a seismic survey off its coast on May 26 and hindered operations of another vessel on June 9, while China accuses Vietnam of illegally entering its waters and putting fishermen’s lives at risk.

Asked if the U.S. had a role to play in the dispute, Vietnamese Foreign Ministry spokeswoman Nguyen Phuong Nga posted a response online on Friday that “every effort by the international community in maintaining peace and stability in the East Sea is welcome,” the term Vietnam uses to refer to waters off its coast.

China feels that such boundary disputes should be settled one—on—one rather than multilaterally, Mr. Wang said, pointing to successful negotiations between China and Vietnam that led to an agreement in 2000 establishing a boundary in the Gulf of Tonkin.

The countries bordering the South China Sea have a long history of diplomatic tussles over the disputed Spratly and Paracel islands, which are claimed all or in part by Vietnam, China, Taiwan, the Philippines, Malaysia and Brunei.

The area has hundreds of uninhabited islands, atolls and reefs which straddle vital shipping lanes, teem with fish and are believed to lie above rich oil and gas reserves. Many of the islands are closer to Philippines, Malaysia or Vietnam than China, though Beijing says its claims to them date back centuries.

Southeast Asian nations would like a multilateral approach to give them more negotiating power with China, said Zhao Gancheng, an expert on Southeast Asian affairs at the Shanghai Institutes for International Studies.

“These countries felt they were comparatively weak and would like to introduce the external forces to balance China,” Mr. Zhao said. “But China doesn’t have conflicting interests with the U.S. on the issue of the South China Sea.”

Filipino officials last week accused China of harassing oil exploration vehicles, firing shots and conducting some construction activities on areas it claims around the Spratlys during six or seven incursions since February. China denied the allegation, and warned neighbours not to conduct such research in its territory.

Such tit—for—tat swipes are the common way of airing grievances, but Hanoi has responded much more angrily to the current uproar. It accuses China of attempting to create new disputed areas in waters within 200 nautical miles of Vietnam’s coast, which are guaranteed as an economic exclusion zone by international law.

China, however, says the incidents occurred near the Spratly islands. It has issued terse warnings for Vietnam to settle down, reminding the country it once ruled for 1,000 years to “read your history” in a patronizing weekend editorial published by the Communist Party.

On Sunday, hundreds of Vietnamese staged a second round of rare protests in Hanoi and southern Ho Chi Minh City, calling for China to stay out of its territory. Demonstrations are typically quashed quickly by police.

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