There are reports of rising prices in the capital.
Haiyan makes landfall
Haiyan earlier swept over Vietnam's Con Co island, 30km (18 miles) off the coast of central Quang Tri province.
"All 250 people on the island, including residents and soldiers, were evacuated to underground shelters where there is enough food for several days," the Tuoi Tre newspaper said.
Boats have been ordered back to port along many coastal regions. Several hundred domestic and international flights have been cancelled. Schools have been closed for Monday in many parts of the north.
The authorities have moved 883,000 people in 11 central provinces to safe zones, according to Reuters.
Some people have complained that the warnings have come too late.