By James Pearson
HANOI, Aug 7 (Reuters) - A Chinese survey ship which has been embroiled in a tense month-long standoff with Vietnamese vessels has headed away from Vietnam's Exclusive Economic Zone (EEZ), a Washington-based think tank said on Wednesday.
Since early July, Vietnamese ships have closely tracked Chinese vessels operating within the Southeast Asian country's EEZ, in the latest confrontation in waters that are a potential global flashpoint as the United States challenges China's sweeping maritime claims.
"Ship tracking data show that China's survey ship has exited the Vietnamese EEZ for now, but at least two of its coast guard escorts remain in the area of the survey," Devin Thorne, senior analyst at the Center for Advanced Defense Studies (C4ADS) told Reuters, citing data from maritime analytics company Windward.
"Vietnamese ships pursued Haiyang Dizhi 8 as it returned to Fiery Cross Reef and now appear to be loitering just outside of Vietnam's EEZ," Thorne added.
Fiery Cross Reef is a man-made island, controlled by China, built on a disputed South China Sea reef, to which Vietnam and the Philippines have competing claims.
It was not clear late on Wednesday if China's Haiyang Dizhi 8 survey vessel planned to return to Vietnam's EEZ, Thorne said.
The survey ship, operated by the China Geological Survey, has been conducting what appears to be seismic survey of Vietnam's offshore oil blocks, according to the Windward data.
U.S. Secretary of State Mike Pompeo has criticised Chinese "coercion" in the disputed South China Sea, while Beijing's top diplomat, Wang Yi, said last week that maritime problems involving Vietnam should not interfere with two-way ties.
The offshore impasse has stoked anti-China sentiment in Vietnam, where previous tensions between Beijing and Hanoi over the disputed waters have erupted into protest.
Last week, a Vietnamese fishermen's group urged the government to take stronger measures to remove the ships, saying they were disrupting fishing activities.
And on Tuesday, Vietnamese police broke up a brief demonstration outside the Chinese embassy in Hanoi against the operations of the vessel and its escorts.
Also on Tuesday, the Philippines, which is also embroiled in maritime disputes with Beijing, said its president Rodrigo Duterte would meet Chinese counterpart Xi Jinping soon to discuss a 2016 arbitration case over the South China Sea.
That ruling in international law invalidated China's claim, based on its so-called "nine-dash line", to historic sovereignty over most of the busy and resource-rich waterway. (Reporting by James Pearson; Editing by Stephen Powell)