Vietnam's Mekong Delta is bracing for the arrival of Typhoon Tembin, which has already left 230 people dead in the Philippines.
Forecasters say heavy rain and strong winds could cause serious damage in the vulnerable region, where facilities are not built to cope with such severe weather.
National television station VTV said several hundred thousand people have been evacuated from their houses, which are mostly made from tin sheets and wooden panels.
In Vung Tau city, thousands of fishing boats halted their months long fishing trips to return to shore.
Typhoons and storms rarely hit the Mekong Delta.
But in 1997, Tropical Storm Linda swept through the region, killing 770 people and leaving more than 2000 others missing.