The fire broke out at around 7 am in a forest area bordering Quang Ninh and Ninh Chau communes, according to local authorities.
More than 300 residents, along with police, military, forest rangers and border guards, were mobilised to contain the fire.
Firefighting efforts were hampered by temperatures exceeding 40 degrees Celsius, strong hot winds and thick dry vegetation, which caused the flames to spread rapidly.
Authorities said the sandy terrain and multiple fire points made access difficult, while limited water supplies forced many crews to create firebreaks manually to stop the blaze from spreading further.
By late evening, emergency teams were still working to fully contain the fire and prevent reignition.
The cause of the wildfire remains under investigation.
