A spare gritter has been brought in after the brick attack
The driver of a gritting lorry narrowly escaped injury when a snowball containing a brick crashed through the window of his vehicle.
A gang of up to 15 youths targeted the Torfaen council vehicle in freezing temperatures at Pontnewydd at 2230 GMT on Monday.
After stepping into the road to slow it down, the gang threw snowballs - one of which contained the brick.
Council spokeswoman Christina Harrhy condemned the attack as "mindless".
Mrs Harrhy said: "The brick crashed through the passenger side window, covering the driver in glass.
"He said it sounded like a bomb had gone off. This mindless act could have caused serious injury.
"Thankfully, apart from being shaken up, the driver is OK.
"The gritter is now out of action but a spare vehicle is now being used on the round."
Mrs Harrhy, Torfaen's head of technical services and performance, said she could not believe anyone would target a vehicle that was trying to keep motorists and residents safe.
"The men do such a great job by working all hours," she said.
"They don't deserve this."
The incident has been reported to Gwent Police.
Ms Harrhy added that, apart from the attack, the gritting operation ran smoothly.
The council reported that since the weekend more than 150 tonnes of salt had been used on roads in the county borough, which could increase to more than 500 tonnes if the bad weather persisted for the rest of the week.
Just over half of the roads in Torfaen had been treated, the council added, including all main routes.