It was the second major flood reported this week in the north.
Abdul Jabar Taqwa, the governor of Takhar province, said flood waters broke through a dam early Friday, washed down a valley and damaged several villages in Ishkamish district.
"It was a very powerful flood. It hit around midnight," Taqwa said. "Dozens of villages have been hit. I'm worried that the death toll will go up."
Taqwa said 17 people were killed in the flooding. Earlier, the governor had received reports of 27 deaths.
He said a delegation from the provincial capital of Taloqan was surveying damage at the scene, and vehicles could only be driven to within a six-hour walk of the flooded area.
He said a delegation from the provincial capital of Taloqan was surveying damage at the scene.
On May 6, another flash flood swept through Dhy Marda village in Sari Pul province, killing 21 people, many of them members of a wedding party.
Sayed Jahangir Kramat, the deputy police chief for the province, said about 45 homes were destroyed and another 150 were damaged in that flood as heavy rains caused floodwaters to rush down the mountains.
Other minor flooding earlier this week in two other districts of Sari Pul province killed three people.