JAKARTA, Indonesia (AP) — Indonesia’s navy said Monday that one of its patrol vessels was rammed by two Vietnamese coast guard ships after intercepting a boat it says was fishing illegally in its waters.

Indonesia detained 12 Vietnamese fishermen from the boat, which sank in Saturday’s clash, and they are being held at a naval base “for further legal proceedings,” said Rear Adm. Yudo Margono, the commander of Indonesia’s Western Fleet. Two others were rescued by Vietnam’s coast guard.

The Vietnamese fishing vessel was intercepted in waters off Indonesia’s Natuna island chain, which is in the southernmost reaches of the South China Sea, Margono said in a statement Monday. Indonesia calls the waters the North Natuna Sea.

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“The location of the arrest was actually in Indonesian waters,” Margono said. “But the Vietnamese also claimed that the area was Vietnamese waters.”

Video purportedly shot from the Indonesian vessel that has been shared widely on social media shows a Vietnamese patrol boat colliding with it as armed Indonesian seamen shout out insults such as “dog,” ″pig” and “you die.”

Indonesia, the world’s largest archipelagic nation, has sunk hundreds of illegal fishing vessels from Vietnam, the Philippines, China and other nations since 2014 as part of efforts to exert greater control over its vast maritime territory.

Its 2017 decision to rename the Natuna waters angered China, which claims most of the South China Sea and is in dispute with many Southeast Asian nations over the competing stakes.

Indonesia doesn’t have a territorial dispute with China, but Beijing’s claims overlap with Indonesia’s internationally recognized exclusive economic zone extending from the Natuna islands.