Dog owners are being warned their pets could be legally shot if found attacking sheep.
The warning comes after 13 sheep were killed and three injured during dog attacks on farms in Worcestershire.
At Hall Garth Farm in Peopleton nine sheep have been killed in five attacks. Owner Sue Tarran said she saw two dogs, thought to be Alsatians, attacking.
A police spokesman said it was in everyone's interest that the attacks are stopped as soon as possible.
Entitled to shoot
Four more sheep were found dead at a farm in Burlingham on 8 March.
A spokesman for Pershore Police said: "We are investigating these incidents along with a report that two Alsatians and a rottweiler were seen loose at Peopleton Rough on 7 March.
"If the owners realise it is their dog or dogs involved in these distressing attacks we urge them to keep them under control.
"Farmers are legally entitled to protect their flocks by shooting dogs that are worrying their sheep."