The Hanoi government ordered Friday the owners of three buildings now under construction to demolish unauthorised stories and pay fines for violating building norms.
Each is expected to lose hundreds of thousands of dollars.
A 21-story building coming up on No 4 Dang Dung Street will have its top four stories dismantled.
A 10-story building in an alley off Nguyen Chi Thanh Street will lose five floors.
A 17-story building on No 9 Dao Duy Anh will lose three stories.
Their owners will have to pay the fines and submit demolition plans by early next month.
The city administration began earlier this year a massive investigation into illegal construction which is said to be mushrooming.