Two pregnant sheep were butchered in a field in Denton in the latest of a series of attacks on animals in the area.
The sheep were attacked sometime between 4pm on Monday, December 28, and 8am the following morning in a field off Horton Road.
After the animals were killed, they were stripped of their meat and their remains were left in the field.
A spokesman for Northamptonshire Police said: “This type of incident has happened a number of times over the past 18 months in the Denton and Brafield-on-the-Green areas.
“I would ask residents to contact the police if they see any suspicious people or vehicles near fields with sheep in them and to call us if they are offered cheap meat not from a butchers.
“In this latest attack, the two sheep were pregnant and would have been terrified. It certainly was not a humane way for them to be killed.”
Anyone who sees unusual activity around fields, including torch light or suspicious vehicles, can call Northamptonshire Police on 101 or the independent charity Crimestoppers anonymously on 0800 555 111.
The same numbers can also be used to report people selling cheap meat in unusual circumstances.