The Gianh river in Quang Binh province reached a record high but was receding slowly, he said.
Nearly 5,000 people were evacuated from their flooded homes to higher ground, Song said, adding that soldiers and police officers were sent to help villagers deal with the floods.
Floods also killed a teenager in Nghe An province, a disaster official there said.
In the neighboring province of Ha Tinh, the floods killed two people and authorities were searching for two others missing there, disaster official Tran Quang Duc said.
One person each was missing in Thua Thien Hue and Binh Dinh provinces, the national floods and storms control department said.
The department said the floods has disrupted traffic on some parts of several highway and parts of the North-South railway in Quang Binh province.