Vietnam has suspended all China flights as part of "strengthening measures" against the coronavirus outbreak, its civil aviation authority said in a statement on Saturday.
The step applies to all airlines "which have routes between Vietnam and China" and also includes Hong Kong, Macau and Taiwan, it added in the directive which was posted on its website and took effect at 1 pm Saturday (0600 GMT).
An AFP correspondent on a flight from Taiwan to Vietnam was among 98 passengers told to disembark just as the announcement went public.
"The decision is ridiculous and unacceptable," Vietnamese tourist Doan Thi Ngoc Diep told AFP after leaving the plane.
Vietnam is the latest country to impose extraordinary travel barriers after the virus spread to two dozen nations and killed 259 people in China where it originated in the city of Wuhan.
The United States temporarily barred entry to foreigners who had been in China within the past two weeks and Australia said it was barring entry to non-citizens arriving from China.
Italy, Singapore and Mongolia have also taken similar sweeping precautions.
The World Health Organization declared the coronavirus outbreak a global health emergency on Thursday but did not advise international trade of travel restrictions.
Vietnam's announcement came after the country confirmed its sixth case of the coronavirus.
A 25-year-old hotel receptionist working in Nha Trang contracted the SARS-like pathogen after coming into contact with Chinese tourists who were later diagnosed with coronavirus.
She was also the first domestic infection for a Vietnamese national with no known history of travel to China.
Three of the country's six cases were Vietnamese nationals who had travelled to Wuhan.
The receptionist's health is "stable, no fever or cough", a hospital staffer told AFP on condition of anonymity, adding she had "no history of travel to China recently".
Vietnam has joined Thailand, China, Germany, Japan, South Korea, France and the United States as the only countries with confirmed domestic coronavirus infections.