A sheep was put down after apparently suffering a severe bite to the neck.
Malvern Hills Conservators said a dog that was loose and out of control attacked four sheep on Castlemorton Common.
The conservators claimed the dog was caught in the act but the dog's owners have denied any wrongdoing.
West Mercia Police is investigating what happened after the complaint over the weekend.
According to the Malvern Hills Conservators, the three other sheep are likely to recover but may lose their unborn lambs through shock.
The conservators warned dog owners that their pets must be kept on a lead or under strict control at all times as farmers have a right to shoot a dog, as a last resort, if it is worrying livestock.
You can check where sheep and cattle are grazing using Stockwatch alerts available at malvernhills.org.uk
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