It said these acts were interfering in particular with "Vietnam's long-standing exploration and production activities" in the waters.
Vietnam on Friday demanded China remove a survey ship from Vanguard Bank, which it says lies within Vietnam's 200-mile exclusive economic zone. While Beijing has protested against USA freedom of navigation exercises in the South China Sea, Washington and China's southeast Asian neighbours are concerned about Beijing's military build-up, reports South China Morning Post.
In May 2014, Chinese and Vietnamese vessels engaged in a unsafe confrontation when China's national oil company moved its oil platform into waters Vietnam considers its territory.More news: Emery confident Arsenal will soon have 'three or four' new players
'Over the last several days, the Chinese survey ship, Haiyang Dizhi 8, and its escorts conducted activities in the southern area of the East Sea that violated Vietnam's exclusive economic zone and continental shelf, ' Vietnamese foreign affairs ministry spokesperson Le Thi Thu Hang said in a statement, according to Aljazeera.
Secretary of State Mike Pompeo said in March this year that China, by blocking development in the South China Sea through coercive measures, was preventing Asean members from accessing more than US$2.5 trillion (S$3.4 trillion) in recoverable energy reserves.
"The United States firmly opposes coercion and intimidation by any claimant to assert its territorial or maritime claims", Ortagus added.More news: White man denies saying 'Go back where you came from'
East Sea is the Vietnamese name for the South China Sea. "China should cease its bullying behaviour and refrain from engaging in this type of provocative and destabilising activity", Ortagus said in a statement.
Vietnam had contacted the Chinese side many times via different channels and handed over diplomatic notes to protest the violations, she said, adding that Vietnam's authorities at sea continued adopting proper measures to enforce the nation's sovereignty and jurisdiction in a peaceful manner in line with worldwide law.
Chinese Foreign Ministry spokesman Geng Shuang, in response to questions for comments about the standoff, said on Wednesday that "We hope the Vietnamese side can earnestly respect China's sovereign rights and jurisdiction over the relevant waters, and do not take any move that may complicate matters".More news: New boss of BMW 'will provide brand with fresh momentum'