A department spokesman said downpours had damaged half a million homes in four central provinces and inundated thousands of hectares of rice fields, inflicting damages running into hundreds of millions of dollars.
Hundreds of villages in the Thua Thien-Hue, Quang Nam, Quang Ngai, and Binh Dinh provinces remain under water.
The latest disaster is the fifth major flood to hit the southeast Asian country since August.
Since October 26, almost 140 people have been killed by floods in central provinces. Cholera has spread rapidly in the flooded regions over the past three weeks, and more than 200 people have tested positive for the infection. No deaths from cholera have yet been reported.
Vietnamese Prime Minister Nguyen Tan Dung has urged local authorities to take emergency action to prevent starvation and disease in the flooded areas, and a nationwide campaign to raise money for the regions is underway. The United States has pledged $900,000 toward relief efforts.
National rail officials said that the line between Hanoi and Ho Chi Minh City, damaged by floods and landslides, will be restored in two days.