Valeriy Zaluzhny told a forum that Ukraine's children needed particular attention "because their fathers have gone to the front and are maybe among the nearly 9,000 heroes who have been killed".
Ukrainian officials have only very rarely given any detail on military losses in nearly six months of war.
The last estimate dates back to April when Ukrainian President Volodymyr Zelensky said that up to 3,000 Ukrainian soldiers had been killed and 10,000 injured.