In several northern provinces, including the suburbs of Hanoi, residents waded through knee-high floods. Brown water cascaded down pedestrian steps.
Landslides and floods triggered by the typhoon have killed at least 141 people in northern Vietnam and 59 others were missing, the disaster management agency said in its latest update on the situation.
Most of the victims were killed in landslides and flash floods, the agency said, adding that 764 people have been injured.
State media reports said the water level of the Red River in Hanoi had been rising 10cm every hour.
At least 3500 households were evacuated in Vietnam's Yen Bai province due to floods after Yagi. (EPA PHOTO)
Some schools in Hanoi have told students to stay home for the rest of the week due to flood concerns, while thousands of residents living in low-lying areas have been evacuated, according to sources, government and state media.
The typhoon made landfall on Saturday on Vietnam's northeastern coast, devastating a swathe of industrial and residential areas and bringing heavy rain that caused floods and landslides. It had previously hit the Philippines and the southern Chinese island of Hainan.
"I have to leave everything behind as the water is rising too fast," said Nguyen Thi Tham, a 60-year-old resident living in the flood-prone area near the Red River in Hanoi. She had only been able to take her dog with her.
She was among a number of people evacuated by boat to a safe shelter early on Tuesday. It was not immediately clear how many Hanoi residents needed to be evacuated.
Several rivers in northern Vietnam have risen to alarming levels, leaving villages and residential areas inundated, according to the disaster agency and state media.
A 30-year-old bridge over the Red River in the northern province of Phu Tho collapsed on Monday, leaving eight people missing.
Authorities across the north on Tuesday subsequently banned or limited traffic on other bridges across the river, including Chuong Duong Bridge, one of the largest in Hanoi, according to state media reports.
"Water levels on the Red River are rising rapidly," the government said on Tuesday in a post on its Facebook account.
Several rivers in Vietnam have risen to alarming levels, leaving residential areas inundated. (EPA PHOTO)
Using loudspeakers that broadcast Communist propaganda in the past, officials warned residents of the capital's riverside Long Bien district to be on alert for possible flooding, and to be ready to evacuate the area.
Other northern areas, including the industrial hubs of Bac Giang and Thai Nguyen, were also facing severe flooding, state media reported. It was not immediately clear if Samsung Electronics and Apple supplier Foxconn, based in Thai Nguyen and Bac Giang, respectively, were affected.
Evacuations were also taking place from flood-prone areas in Bac Giang province, the government said, where the typhoon and floods have caused damage estimated for now to be worth 300 billion dong ($A18.2 million).
More than 4600 soldiers have been deployed in the province to support the evacuation and support flood victims.
Vietnam's foreign ministry asked China to notify it ahead of any release of dam water upstream.
Lao Cai province has reported the highest casualties, with 19 people killed and 36 missing, mostly in landslides, according to the disaster management agency.
The government has yet not provided estimates of the cost of the damage caused by the typhoon, but residents in the coastal cities of Haiphong and Quang Ninh, where the storm first hit Vietnam, said they "lost everything".
Floods have also inundated 162,828 hectares and 29,543 hectares of cash crops and damaged nearly 50,000 houses in northern Vietnam, according to the agency.
