After a four-week stand-off, a Chinese vessel has headed away from Vietnam's Exclusive Economic Zone (EEZ), a Washington, D.C.-based think tank said Wednesday.

Devin Thorne, a senior analyst at the Center for Advanced Defense Studies (C4ADS), referring to data gathered by the maritime analytics company called Windward, said that "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.”

"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. It is not known if China plans to return to Vietnam’s EEZ. Windward data indicated that the ship was conducting seismic activity surveys on Vietnam’s offshore oil blocks.

The man-made Fiery Cross Reef is controlled by China and is located about halfway between the Philippine Island of Palawan and the east coast of Vietnam in the South China Sea. Both countries lay claim to the waters while China uses the historical Nine-Dash Line to claim the bulk of the entire sea including the EEZs of Vietnam and the Philippines.

Previous spats between China and Vietnam have ended in protests and this latest event has done nothing to quell anti-China feelings in Vietnam. The government was asked by a Vietnamese fishermen group to take more effective means to drive the Chinese ships away as they were upsetting their fishing activities. The China embassy in Hanoi was the site of a demonstration Tuesday that police had to break up.

Aerial picture of Chinese ships building artificial islands in the South China Sea
An aerial photo taken though a glass window of a Philippine military plane shows the alleged ongoing land reclamation by China on mischief reef in the Spratly Islands in the South China Sea, west of Palawan, Philippines, May 11, 2015. REUTERS/Ritchie B. Tongo/Pool

In what may or may not be a coincidence, the Philippines announced that President Rodrigo Duterte would meet with Chinese leader Xi Jinping to discuss a United Nations arbitration ruling that did not go in favor of China. The ruling invalidated China's claim based on the Nine Dash Line and historic sovereignty over most of the busy and oil-rich waterway inside the Philippine’s EEZ.

China is engaged in a fierce trade war with the United States and is not unaware that the USS Ronald Reagan aircraft carrier is ready and waiting in the Philippines waters as events unfold. U.S. Secretary of State Mike Pompeo has been critical of Chinese "coercion" in the disputed South China Sea. Beijing's top diplomat, Wang Yi, said last week that maritime problems involving Vietnam should not interfere with two-way ties.