"Vietnam sincerely wishes for countries' legitimate, justifiable rights and interests in accordance with the United Nations Convention on the Law of the Sea (UNCLOS) to be respected," the ministry’s spokeswoman Le Thi Thu Hang said in a statement.

She was commenting on reports that Chinese survey ship Haiyang Dizhi 8 was spotted inside sea areas about 352km away from Bruneian and Malaysian coasts by ship tracking website Marine Traffic on April 16.

The Haiyang Dizhi 8 was tagging Malaysian exploration vessel West Capella, belonging to state oil company Petronas, in the East Sea, known internationally as the South China Sea, on April 17, Reuters reported. The Haiyang Dizhi 8 was flanked at one point by more than 10 Chinese vessels, it said.

Vietnam, as a country in the East Sea and an ASEAN member, is closely monitoring the situation, Hang said. She said relevant parties have the responsibility to abide by international law and UNCLOS and show their commitment to developing friendly relationships between countries, as well as maintaining peace, stability and cooperation in the East Sea, the region and the world.

Earlier, on April 14, citing data from Marine Traffic, Reuters had reported that the Chinese survey vessel had appeared at 158 km (98 miles) off Vietnam’s coast, within Vietnam’s Exclusive Economic Zone (EEZ). It was accompanied by at least one Chinese coast guard vessel, the report said.

The Haiyang Dizhi 8 and its Chinese escort vessels had previously violated Vietnam's EEZ and continental shelf in the southern parts of East Sea last July. It left the area last October.

Vietnam has consistently opposed the actions of the Chinese vessels.

The Chinese ship's presence has been criticized by the U.S. State Department, Defense Department and senators.

On April 17, the U.S. State Department had said China should cease its "bullying behavior" and "provocative actions" aimed at offshore oil and gas developments by other countries in the South China Sea.

China’s actions threaten regional energy security and undermine the free and open Indo-Pacific energy market, it said.