Asia's most powerful typhoon this year, Yagi brought gales and heavy rain as it moved westwards after landfall on Saturday, collapsing a bridge this week while scythed through provinces along the Red River, the area's largest.
"This is the worst flood I have seen in 30 years," Hanoi resident Tran Le Quyen, 42, told Reuters, adding that she had to move furniture from her flooded home to higher ground.
"It was dry yesterday morning. Now the entire street is flooded. We couldn't sleep last night."
The typhoon and subsequent landslides and floods have killed 152 people, while 140 were missing, the government estimated.
Some schools in Hanoi have told students to stay home for the rest of the week, while thousands of residents of low-lying areas have been evacuated, government and state media said.
"My home is now part of the river," said Nguyen Van Hung, 56, who lives in a neighbourhood on the banks of the Red River.
Nearer the city centre, charity Blue Dragon Children's Foundation had to evacuate its office on Tuesday, after authorities warned of flood risks.
"People were moving frantically, moving their motorbikes, relocating items," said spokesperson Carlota Torres Lliro, expressing concern for dozens of children and families living in slum areas and makeshift houses by the river.
BLOW TO FACTORIES
Yagi wreaked havoc on many of factories and flooded warehouses in coastal export-oriented industrial hubs east of Hanoi, forcing closures, with some only expected to resume full operations after weeks, executives said.
The disruptions threaten global supply chains as Vietnam hosts large operations of multinationals that ship mostly to the United States, Europe and other developed nations.
Elsewhere, in provinces north of the capital, landslides triggered by heavy floods killed dozens.
"My house's first floor is completely under the water," said Nguyen Duc Tam, a 40-year-old resident of Thai Nguyen, a city about 60km from Hanoi.
"Now we have no fresh water and electricity," he added.
Among the factories housed on the outskirts of the city, which has a population of about 400,000, is a large facility for Samsung Electronics.
From Vietnam, the South Korean company ships about half of its smartphones worldwide.
There were no signs of flooding at the facility on Wednesday, a Reuters witness said.
"For more than 20 years that I've lived here, I've never seen such historic flooding," said Hoang Hai Luan, 30. "My properties and possibly those of many others are completely lost."
