The fire started just before midnight on Tuesday (1700 GMT) in the parking floor of the 10-storey building, witnesses said, an area packed with residents’ motorbikes.
“Authorities have rescued about 70 people, rushing to hospital 54 people, including dozens of dead,” the official Vietnam News Agency said.
“This is a very serious fire,” the statement said.
The blaze was out on Wednesday morning, although workers continued searching for survivors.
Rescuers struggled to access the building, in a highly residential area of southwest Hanoi, located down a narrow alley.
“We could not help them much,” a woman, who gave only one name Hoa and lives near the block, told AFP at the site.
“The apartment is so closed with no escape route, impossible for the victims to get out.”
It comes a year after a blaze in a three-storey karaoke bar in commercial centre Ho Chi Minh City killed 32 people.
As many as 17 people were also injured in that fire, with the owner arrested on charges related to breaching fire prevention regulations.
Vietnam has experienced several deadly fires in recent years, frequently at entertainment venues like popular karaoke bars.
