The police were alerted at 23:00 local time that many people were trapped inside the burning premises. The rescue service managed to get seven people out alive, two of whom were taken to hospital with injuries.
Images in Vietnamese media show the soot-covered multi-story building in western Hanoi, largely destroyed by the flames.
"The police suspect that the bar was deliberately set on fire," says the local police in a statement. One person has been arrested.
Two years ago, 32 people died in a major fire at a karaoke bar in Ho Chi Minh City. The incident shocked Vietnam and led to more than two-thirds of the country's approximately 15,000 karaoke bars being forced to close due to non-compliance with fire regulations.
Six people, including four police officers, were sentenced to prison in October for their involvement in the fire.
