The eye of the storm is now heading into Danang and Quang Nam provinces, according to meteorologists.
Initial reports show the storm brought down trees, pelt off roofs and broke windows of high-rise buildings in Da Nang City.
Hue City has been flooded.
No casualties have been reported.
In Da Nang, Hue and Hoi An, local residents spent a sleepless night in darkness to reinforce their houses and public works.
Minister of Agriculture and Rural Development Cao Duc Phat also stayed awake the whole night, instructing storm prevention work.
Phat warned local people should stay indoors to avoid unexpected injuries.
Vietnam Airlines has cancelled more than 20 flights from Hue and Da Nang airports.
Some first pictures of the storm Nari in central Vietnam:
A wall blown out by wind in Da Nang.
In Da Nang this morning.
Flood in Hue City this morning.
In Quang Nam province.
Fallen trees on the street of Hue City this morning.
Trees and electric poles fall in Da Nang this morning.
The Han River, Da Nang, this morning.
In Da Nang.
Rain and strong wind began attacking Da Nang last night.
Big waves in Ly Son Island, Quang Nam province.
Flood in Hoi An.
The iron door of a parking-lot in Hue City collapsed in storm.
What the stars mean:
★ Poor ★ ★ Promising ★★★ Good ★★★★ Very good ★★★★★ Exceptional