Vietnam is still reeling from the impact of Typhoon Yagi, the strongest storm to hit Asia this year, which made landfall on Saturday. At least 197 people have been killed and 128 missing since the storm struck, according to the government's disaster management agency. Some 800 people have been injured.
"High flooding water levels have flooded riverside and low-lying areas, eroded dykes and threatened parts of Hanoi and other northern provinces," the agency said in a report.
The city had earlier evacuated thousands of people living near the swollen river as its waters rose to a 20-year high.
North of Hanoi, deadly landslides and severe floods are still affecting several areas, according to state media reports.
"I never thought my house would be under water this deep," said Hoang Van Ty outside his home in Thai Nguyen province.
"My clothes and furniture are all under the water. Many things were floating around too but luckily I closed the doors so nothing was washed away."
Thai Nguyen province is home to Samsung Electronics' largest smartphone manufacturing plant in Vietnam. Flood waters have receded in some parts of the province, where clean up efforts are now taking place.
The landslides and floods have inundated more than 200,000 hectares of rice and cash crop fields, according to the disaster management agency.
The typhoon has also disrupted power supplies and blown off roofs of several factories in Haiphong and Quang Ninh provinces, halting their production.
Several countries, including Australia, Japan and the United States, have announced that they were sending aid to Vietnam.
