Chinese research and escort vessels persisted in Vietnam's exclusive economic zone (EEZ), neighboring gas fields managed by Russian entities in the South China Sea, undeterred by Vietnam's request for their departure.

Chinese ship Xiang Yang Hong 10, along with its escort vessels, has been operative within the confines of Vietnam's EEZ since May 7. This incursion, according to Ray Powell of Stanford University's Project Myoushu, which focuses on the South China Sea, is the most serious since 2019, pointing to a "worrying escalation" in tensions between the two countries.

Much of the energy-rich waters of the South China Sea, encompassing sections of Vietnam's EEZ, have been claimed by China. A 2019 confrontation in the area persisted for over three months and was primarily aimed at a block then managed by Rosneft, a Russian state oil company. Later, Rosneft transferred its South China Sea assets to Zarubezhneft, another state-owned Russian enterprise, currently operating some of the gas fields implicated in the ongoing dispute.

In the weeks since the Chinese research vessel's arrival, it has been navigating predominantly across gas block 04-03, which is managed by Vietsovpetr-a joint venture between Zarubezhneft and PetroVietnam-as per the South China Sea Chronicle Initiative (SCSCI), a non-profit, independent vessel-tracking initiative. The vessel also traverses blocks 132 and 131, which Vietnam has authorized Vietgazprom, a collaboration between Russia's Gazprom and PetroVietnam, to explore. Notably, China has also submitted competing bids to explore these two blocks.

In response to the enduring standoff, Mao Ning, spokesperson for China's foreign ministry, maintained that China held sovereignty over the Spratly Islands and its adjacent waters and jurisdiction over the relevant waters. She deemed the Chinese vessels' activities as "legitimate and lawful," dismissing the claim of trespassing into other nations' EEZs.

Mao emphasized China's communications with concerned parties on the issue and its intention to "jointly safeguard the peace and stability of the South China Sea." She also asserted China's commitment to defend its "lawful rights and interests."

Vietnam issued a public demand for the departure of Chinese vessels on Thursday when they were stationed in block 129, managed by Vietgazprom, Powell noted. This demand followed a visit by Dmitry Medvedev, former Russian President and current deputy chairman of Russia's security council, to Hanoi on Monday.

Vietnamese fisheries vessels shadowed the Chinese fleet from a distance of 200-300 meters on Friday, Powell reported. The Chinese ships had moved to a block neighboring those operated by Russian firms, despite international norms allowing ships to traverse other nations' EEZs, an act which Vietnam and other claimants in the South China Sea, including the Philippines and Malaysia, perceive as aggressive.