It said in a statement Wednesday that the incident "undermines the potential of a genuinely deep and trusting regional relationship between the Association of Southeast Asian Nations (ASEAN) and China."

It is crucial that such incidents be avoided and that differences be addressed in a manner that enhances dialogue and mutual trust, the statement said.

The statement was referring to the deliberate ramming and sinking of a Vietnamese boat carrying eight fishermen by a Chinese coast guard vessel on April 2 as the former were fishing off Phu Lam (Woody) Island in Vietnam’s Hoang Sa Archipelago (Paracel Islands) in the East Sea, known internationally as the South China Sea.

Earlier, U.S. State Department spokesman Morgan Ortagus had said the U.S. was "seriously concerned" about the incident. He called China’s action an assertion of "unlawful" claims.

Vietnamese Foreign Ministry spokesman Le Thi Thu Hang has demanded that China investigates the incident and "take strict action against the Chinese vessel and refrain from repeating such acts in future as well as pay proper compensation for the damage caused to the Vietnamese fishermen."

The Quang Ngai’s Fisheries Society said that after sinking the Vietnamese boat, the Chinese vessel had picked up eight Vietnamese fishermen and taken them to the Woody Island. Upon receiving news of the sunken ship, three other Vietnamese fishing boats tried to rescue then, but were chased away by the Chinese vessel. Two of the vessels were captured and towed to the island.

At 2 p.m. April 2, China released the two fishing boats and eight fishermen. A day later, Vietnamese authorities received the detained Vietnamese fishermen safely.

On the same issue, Vietnam has rejected and protested China sending two diplomatic notes to the U.N., laying claim to Vietnamese territories in the East Sea.

China seized the Paracel Islands from South Vietnam by force in 1974, and has since been occupying them illegally.

In 2014 China brought an oil rig, Haiyang Shiyou 981, and installed it in waters off the Paracel Islands, changing the status quo in the waters. Since then, Chinese ships have chased after and rammed many Vietnamese fishing vessels near the islands in Vietnamese waters.