By Agencies

Casualties include four families whose houses were buried in a landslide early Thursday while they were sleeping.

At least 37 people were killed and another 40 are missing as floods and landslides ravaged northern and central Vietnam.

The disasters injured 21 people and destroyed or damaged more than 1,000 houses, submerged another 16,740 homes and damaged infrastructure and crops in six central and northern provinces, the Vietnam Disaster Management Authority said in a statement on Thursday.

In the hardest-hit northern province of Hoa Binh, 11 people died and 21 others were missing.

"It's impossible to fight against this water, it's the strongest in years," Ngo Thi Su, a resident in Hoa Binh, was quoted as saying by state-run Vietnam Television (VTV).

Casualties include four families whose houses were buried in a landslide early Thursday while they were sleeping, killing six and leaving another 12 missing, disaster official Quach Viet Hoang said.

"We are mobilising all forces to search for the missing," a disaster official in the province told AFP news agency by phone.

A terrified resident described severe flooding in other parts of the province, where a state of emergency was declared.      

"The flash flood was terrible. Water poured down from the hill, like a surge three metres high," Phan Ba Dien told state-controlled VNExpress news site. 

Evacuations were ordered for 200,000 people in Ninh Binh province in the north.

A tropical depression hit central Vietnam on Tuesday and brought heavy rains.

More rain is forecast for some parts of northern and central regions as a cold spell is moving from southern China to Vietnam, the disaster agency said.

Agriculture Minister Nguyen Xuan Cuong was quoted as telling a government emergency meeting Wednesday it was the first time in a decade that northern and central regions suffered such a large volume of rain in a short period of time.

Rain of up to 50cm was reported over the three-day period until Wednesday in some parts of central and northern regions.