The communist government has ordered local authorities to mobilise the army and police to rescue trapped residents following heavy downpours, state-run Vietnam Television reported.
The channel said at least 11 had died in the flooding with some 27,000 homes under water in the region.
Local official Nguyen Huu Hoai told AFP that the death toll was seven in Quang Binh province, but added that conditions were improving.
"We can reach areas which were isolated by flooding," the chairman of the provincial People's Committee told AFP.