Thousands of homes near Hanoi were under several feet of water Thursday after a portion of a dike holding back the storm-swollen Red River burst.
About 80,000 people were forced to flee.
The dike broke Wednesday in Vinh Phu province, about 30 miles northwest of Hanoi, the English-language Vietnam News reported.
More than 10,000 other people had already been left homeless further north in Lai Chau and Son La provinces, near the Laos border, due to flash floods and landslides caused by several days of heavy rain.
Most of northern Vietnam’s rivers are at or above flood levels, according to the official Vietnam News Agency.
The level of the Red River where it passes through Hanoi was down slightly Thursday morning because of the break upstream in Vinh Phu. But thousands of homes outside of Hanoi’s dike system and in villages near the city were already under several feet of water.
Residents rented rowboats to carry valuables to dry land for storage with friends and relatives. With Typhoon Niki approaching from the South China Sea, radio broadcast repeated warnings for residents to evacuate low-lying areas.