Chagee milk tea is the latest high-profile brand to fall foul of diplomatic tensions over competing territorial claims in the strategic waterway, after Hollywood blockbuster "Barbie" and a range of popular children's dolls.

Police in commercial hub Ho Chi Minh City are investigating Chagee about a map on its website showing the "nine-dash line" marking Beijing's claims in the South China Sea.

The city's Department of Culture and Sports said late on Thursday that, together with city police, they have been "working with Chagee Vietnam to clarify the matter".

In the official statement, authorities also asked "individuals and organisations to use official maps, so as not being abused with distorted information on national island sovereignty".

Chagee had been due to open a large branch in central Ho Chi Minh City but state media reported that all logos and signage were removed on Monday night as the row broke out.

The South China Sea is home to valuable oil and gas deposits and crucial shipping lanes, and several of China's neighbours have voiced concern that Beijing is seeking to expand its reach.

Beijing has long used the so-called line to justify its claims over most of the resource-rich South China Sea, often to the annoyance of Vietnam, which also claims parts of the strategic waterway.

Vietnamese authorities have been quite sensitive about the topic. In recent weeks, Chinese-made "Baby Three" dolls have been pulled from shops over a facial mark supposedly resembling the nine-dash line, which appears like a distorted U-shape.

"Barbie", the fantasy comedy film directed by Greta Gerwig and starring Margot Robbie and Ryan Gosling, was banned from cinemas in Vietnam in 2023 due to scenes featuring the nine-dash line.