More than 100 people were dead or missing in flash floods and landslides as heavy rains brought by tropical storm Kammuri pounded mountainous northern Vietnam, officials said Saturday.

At least 72 people have died and 37 are missing since the storm hit the poor and widely deforested region on Friday, having previously lashed Hong Kong and southeastern China, said central and provincial emergency services.

Worst hit was Lao Cai province near the Chinese border, where at least 36 people died and 32 were missing, hundreds of houses were destroyed or damaged, and transport links were cut, isolating some areas, emergency officials said.

"Landslides have hit many areas, but flash floods have caused the largest number of deaths," said Pham Van Quang, an official with the provincial flood and storm control committee. "It's still raining hard here.

"At least 800 houses have been destroyed or damaged. We are still trying to get in touch with local authorities to help the people there. Rescue efforts are ongoing but they are being slowed by the severe weather."

State-run VTV showed residents in Lao Cai moving on wooden canoes through a town where flood waters reached the roofs of one-storey houses.

Quang said that authorities were updating the figures of dead and missing, but that they had no contact with some districts because of damaged telephone lines and cut-off roads, including the "completely isolated" Bat Xat district.

At least 25 people died and four were missing in neighbouring Yen Bai province, said emergency services official Nguyen Thi Hai Yen, who said the Red River that also flows through the capital Hanoi had swollen dangerously.

Photographs on the VietnamNet online news site showed pictures of three trains that were stranded by flooding in Yen Bai, halfway between Hanoi and Lao Cai.

In coastal Quang Ninh eight people died, including a five-year-old boy whose family home was buried in a landslide, and seven construction workers whose roadside tent was buried under an avalanche of mud and rocks.

Three people died and one person was missing in Phu Tho province, where TV images showed residents cowering on the roofs of their flooded houses, waiting for rescue workers to reach them by boat.

VietnamNet reported that soldiers were joining rescue activities to bring water and instant noodles to flood victims in several provinces.

The communist central government sent an urgent message ordering local authorities to take steps to cope with flash floods and landslides and to protect the extensive river and coastal dyke system.