"China’s recent aggression in the South China Sea is a disturbing demonstration of a country openly flouting international law. Under the United Nations Convention on the Law of the Sea, China’s actions constitute a violation of Vietnamese sovereignty and its legitimate rights within its exclusive economic zone (EEZ)," Representative Eliot L. Engel, Chairman of the House Committee on Foreign Affairs, said in a statement.

The South China Sea is known as the East Sea in Vietnam.

"Since reports broke last week that Chinese oil exploration ships have entered Vietnam’s EEZ, Vietnam has made repeated requests for their removal - requests that China has willfully ignored.

"This kind of harassment is a threat to Vietnam and evidence of China’s willingness to bully its neighbors. Incidents like this demonstrate China’s blatant disregard for international law and diplomacy," he said.

Vietnam's Foreign Ministry spokeswoman Le Thi Thu Hang on July 19 had said "the Chinese survey ship, Haiyang Dizhi 8 and its escorts have conducted activities in the southern area of the East Sea that have violated Vietnam’s EEZ and continental shelf as established in the provisions of the 1982 United Nations Convention on Law of the Sea (UNCLOS), to which Vietnam and China are signatories."

The activities of China have attracted international attention and criticism.

"I stand with Vietnam and our regional partners in condemning this aggression. The international community must continue to uphold the rules-based order and international law. I call on China to immediately withdraw any and all ships from the territorial waters of its neighbors, and to put an end to these illegal bullying tactics," Engel said.

The U.S. Department of State said July 20 that it was concerned by reports of China’s interference with Vietnam and other countries' oil and gas activities.

It called Chinese acts "bullying," saying that China’s reclamation and militarization of disputed outposts in the waterway, including the use of maritime militia to intimidate, coerce, and threaten other nations, undermine the peace and security of the region.

China claims almost the entire South China Sea, including waters close to Taiwan and Southeast Asian countries Brunei, Indonesia, Malaysia, the Philippines, and Vietnam.

Responding to press inquiries about Vietnam’s actions following China sending out its oil survey vessel Haiyang Dizhi 8 and escorts that infringed on Vietnam’s EEZ and continental shelf, Hang said on Thursday the case was "serious."

Vietnam has contacted China on multiple occasions via different channels, delivered diplomatic notes to oppose China's violations and staunchly demanded that China stop all unlawful activities, withdraw its ships from Vietnamese waters and respect Vietnam's sovereign rights and jurisdiction over its waters, which would serve the interests of bilateral relations as well as regional stability and peace.

Vietnamese authorities at sea have employed a range of appropriate measures to exercise Vietnam’s sovereignty, sovereign rights and jurisdiction in a peaceful and lawful manner for safeguarding Vietnamese waters, Hang added.

Dr. Irina Anatolyevna Umnova, head of the Russian State University of Justice’s Faculty of Constitution and Law Research under the Supreme Court of Russia, told VnExpress Wednesday that Vietnam should seek support from the international community to protect its rights in the South China Sea.

The international community should tell China to respect the rights of relevant parties, come to the negotiating table and follow international law, she said.

Umnova referred to the Philippines’ suit against China in the Permanent Court of Arbitration for its controversial nine-dash line in 2013 and the tribunal ruling in the Philippines’s favor in 2016 as a peaceful method to get the international community to focus on South China Sea issues.