Dogs have killed a ewe and five lambs near Morpeth, with many more left injured.
The incident happened between midnight and 8am on Saturday in fields in Angerton and Hartburn.
Two dogs attacked and killed six sheep, and more than 20 sheep and lambs were injured.
One of the dogs is described as a silver grey lurcher-type, while the other was a short skinned black dog, bigger than a terrier, but smaller than a labrador.
They were seen at around 9am later on the same day near to Angerton Station.
Police are carrying out enquiries to trace the owners of the dogs and are keen for them to get in contact.
Anyone with information about the incident, or who the owners are, should contact Northumbria Police on 101, ext 69191, quoting reference 317 180415. Alternatively, call Crimestoppers anonymously on 0800 555111.
Dog owners have been reminded to make sure their pets are kept under control at all times, in particular when near farmland and other animals.