Sue Heard, who owns Ifton Beech Shropshire Sheep, said her flock was attacked by two Japanese Akita dogs while they were in a field at The Sarn, between St Martins and Gobowen.
She said: "We have a flock of 11 very shocked tups, boy sheep, many with bite wounds.
"They were being kept on land we rent and thankfully the lady we rent from heard dogs barking and went outside to see what was happening, and she saw one of the dogs dragging one of the sheep around. She had to go and shout at them to scare them off.
"She's a dog person and she said she knew they were dangerous and wouldn't have wanted to get too close. They are very large dogs. She went back inside after scaring them off and called me and the police.
"The dogs had dragged two sheep around by their throats before they left and a vet was called to treat those wounds. One of the tups which was bitten has now died.
"Luckily we've just finished lambing and all our ewes and lambs are on our own field.
"But sadly after the dogs were scared away from our sheep they attacked and killed two in-lamb ewes at a farm a couple of fields away. I understand that the scene they left there is pretty horrific."
The tups were taken back to the farm's lambing shed later the same day. While one died, the rest are now recuperating well.
Mrs Heard said: "Nothing like this ever happened before. We've never seen these dogs before and there was no sign of their owner.
"I would ask anyone who knows who owns the dogs to please tell the police because these dogs need to be got rid of. If they've run around killing then they'll do it again. What would happen if they come across someone walking a smaller dog in the countryside?
"It has been emotionally draining, has cost financially in terms of vets fees and time not working and of course, most importantly, the sheep all suffered horrific distress and pain."
Police are now appealing for witnesses to the attack or for any information on the dogs or their owner.
The Akita is a hardy breed of dog from the mountainous regions of northern Japan. The breed is known to be reserved with strangers and intolerant of dogs of the same sex.
Anyone with information on the dogs is asked to call West Mercia Police on 101 quoting the incident reference number 217S of March 2. Alternately anyone can supply information anonymously on the Crimestoppers number 0800 555111.