Vietnam, September 29: The storm, packing winds up to 144kmh, hit central Vietnam, on Tuesday afternoon bringing down trees and powerlines around the cities of Hue and Danang.
Earlier flights to and from both cities were cancelled while residents in the area reinforced their homes and carried valuable items to shelter.
More than 170,000 people have been evacuated from the areas considered most at risk.
Fishing boats in the area have been ordered to return to port.
Ketsana was upgraded to a typhoon shortly after moving over the Philippines into the South China Sea.
Forecasters have said winds are likely to strengthen as the typhoon makes landfall and there is concern that it could cause severe flooding.
As a weaker tropical storm, Ketsana battered the Philippines over the weekend, bringing heavy rains and flooding that left at least 240 dead and nearly 400,000 homeless.
—Agencies