Experts said Vietnam used the US-Filipino drills to distract and weaken China on the South China Sea issue by seizing a Chinese ship.

Vietnam's coast guard on Thursday seized a Chinese oil tanker carrying 100,000 liters of oil which it claims intruded into Vietnamese waters, Reuters reported Monday, adding that it was impounded in the northern port of Hai Phong.

Vietnamese media deliberately played up the seizure to increase tensions in the waters and pressure China while some senior officials manipulated the media to generate nationalism within the country and incite their nationals to hate China, Chen Xiangmiao, a research fellow at the National Institute for the South China Sea, told the Global Times on Monday.

"Even if the US and Vietnam disagree on many issues, Vietnam uses the drills and power of the US to incite, distract and weaken China on the South China Sea issue," Chen said.

Tensions over territorial and maritime disputes between China and Vietnam in the South China Sea have flared up since May 2014 when Chinese and Vietnamese vessels clashed, following a Vietnamese attempt to stop China from installing a deepwater drilling rig near the Xisha Islands, which are controlled by Beijing but also claimed by Vietnam.

"Vietnam is contradictory. On one hand, it seeks cooperation with China, but on the other adopts a tough position against China on the South China Sea issue," said Gu Xiaosong, an expert on Southeast Asian studies at the Guangxi Academy of Social Sciences.