Both geologically and geographically, the Tu Chinh-Vung May (Vanguard-Rifleman) banks belong to Vietnam's continental shelf, Associate Professor Nguyen Chu Hoi, former deputy head of the Vietnam Administration of Sea and Islands, said at a conference in Hanoi Monday.

The continental shelf refers to ledges projecting from the land into and under the sea, and the basic principle is that it is a continuation of land territory into the sea. As such, it is not geographically a part of Vietnam's Truong Sa (Spratly) Islands, Hoi said.

He explained that geographically, there exists a large trench running along the northeast-southwest axis in the deep-water structure of the East Sea. Upon reaching the waters off Da Nang, it runs parallel to Vietnam's coast before running northeast toward Scarborough Shoal and into the Pacific Ocean. This trench therefore separates the Spratly Islands from Vietnam's continental shelf, where the Vanguard and Rifleman banks are, Hoi added.

He added that the trench, which is up to 4,000 meters deep, forms a 2,000-square-kilometer undersea where the international sea route passes through and is 36 kilometers (22 miles) from Vietnam's Con Dao Island. In this plain, the Vanguard-Rifleman area is believed to have large reserves of oil and gas.

Vanguard Bank is a coral reef that lies in the southern part of the East Sea, internationally known as the South China Sea, about 160 nautical miles from the beach of Vietnam’s Vung Tau and about 600 nautical miles from China’s Hainan Island.

Monday’s conference, titled "Vietnam's legal rights and interests in the East Sea under international law," was organized by the Vietnamese Communist Party's online newspaper and was attended by experts and representatives from the Ministry of Foreign Affairs, the Communist Party's Central Propaganda Department and the High Command of Vietnam Coast Guard.

Hoi said that after looking through official documents of the International Hydrographic Organization (IHO), a U.N.-recognized authority on hydrographic surveying and nautical charting, as well as other international geographic documents, he found no evidence showing that the Vanguard-Rifleman banks were part of the Spratly Islands.

"If they say Tu Chinh Bank belongs to the Truong Sa Islands then this proves there is a misunderstanding in terms of geography, geology and the characteristics of the East Sea's seabed," he said.

The associate professor also said that Vietnam has made a joint submission with Malaysia to the United Nations' Commission on the Limits of the Continental Shelf for a possible expansion of the continental shelf in two areas, including one in southeastern part of the East Sea.

"Therefore, Vietnam's continental shelf not only includes Tu Chinh but also expands to the southeast, as stated in Vietnam's submission."

Dr. Tran Cong Truc, former head of the government's Border Committee, noted that legally speaking, the Permanent Court of Arbitration had ruled in 2016 that Vanguard Bank is not a part of the Spratly Islands. The 2016 ruling was issued after the Philippines instituted arbitral proceedings against China for misinterpreting and misapplying the 1982 United Nations Convention on the Law of the Sea (UNCLOS) in order to claim most of the South China Sea with its nine-dash line.

Speaking to VnExpress last July, Truc said the arbitration court’s ruling stated that banks that are far away from the Spratly Islands and separated from it by coral reefs cannot be counted as part of the Spratly Islands.

As Vietnam's Tu Chinh (Vanguard), Huyen Tran (Alexandra) and Phuc Nguyen (Prince Consort) banks all meet these criteria, they are not part of the Spratly Islands, Truc said.

In southern part of the East Sea, including areas around Tu Chinh, Qua Duong (Grainger) and Huyen Tran banks, Vietnam has been constructing a series of rigs and carrying out oil and gas exploration and exploitation activities.

This is in line with regulations on the rights and duties of coastal states as stated under articles 60 and 80 of UNCLOS, which give Vietnam the exclusive right to construct and to authorize and regulate the construction, operation and use of artificial islands, installations and structures for economic purposes in its exclusive economic zone (EEZ) and continental shelf.

The experts' claims reaffirmed an October 3 statement by foreign ministry spokeswoman Le Thi Thu Hang, that Tu Chinh Bank belongs to Vietnam and is not a disputed feature.

Hang made the statement following reports that Chinese oil survey vessel Haiyang Dizhi 8 and escorts had been operating illegally in Vietnam’s exclusive economic zone (EEZ) and continental shelf in the southern part of East Sea since early July.

In the statement, she flatly dismissed her Chinese counterpart's claim that the reef belongs to China and Vietnam must stop oil and gas exploitation activities there.

Discussing Vietnam's possible responses, Truc recommended that Vietnam carefully studies its options if it plans to sue China. Hanoi needs to have a thorough preparation of documents and have a team of lawyers that are fluent in foreign languages and capable of debating in international courts.

He said: "We should not make generic statements and exhortations."

Hoi said Vietnam needs to resolutely pursue its rights in accordance with international law and respect UNCLOS's regulations. The country must also support its fishermen so they are able to continue staying in the sea, connect with each other and carry out their rights.

He stressed: "Vietnam needs to prove to the international community that we may be a small country but we are not weak."