Four lambs were decapitated in Newent, Forest of Dean over the weekend and police are appealing for information.
The carcasses had been removed and the heads left in situ in the field in Malswick.
It is believed that the incident happened overnight between 8pm Friday 19 May and 5pm Saturday 20 May.
There had been 16 sheep in a paddock on a farm, and the others have since been moved to a different location.
Police are investigating and asking for anyone who has information on what happened to come forward.
If you see suspicious activity taking place and offenders are present or nearby, call police immediately on 999.
Officers from the Neighbourhood Policing and Rural Crime teams are now taking part in additional patrols and liaising with local farmers to raise awareness of this issue.
Information can be provided to police online by completing the following form and quoting incident 331 of 20 May: www.gloucestershire.police.uk/tua/tell-us-about/cor/tell-us-about-existing-case-report/
