Police believe a high-powered rifle was used to shoot sheep at a property on the outskirts of Lismore in south-west Victoria.
Camperdown police Senior Sergeant Bill Caldow said he travelled to the property just south of Lismore twice in the past two days to conduct investigations.
He said six sheep were shot and killed between December 23 and 27 and another six were that badly injured they had to be euthanised.
"It's very concerning behaviour. We will be conducting patrols in the area," he said.
The property where the sheep were shot is inside the town's 80kmh speed restriction signs and just south of the Lismore Recreation Reserve.
Senior Sergeant Caldow said it was suspected a high-powered rifle was used to shoot the sheep and the offender or offenders had to go onto the property to commit the offences.
"This is very much an active investigation. We are vigorously pursuing a number of lines of inquiry. It's very concerning," he said.
"We are requesting that anyone with information contact the Camperdown police station on 55931000 or Crime Stoppers immediately on 1800 333 000."
The sheep have been valued at $100 each.
A police spokesman said the incident was highly unusual and police needed public assistance to try and solve the crime.
