A farmer is calling in sharpshooters to deal with a big cat believed to be responsible for destroying 28 of his pedigree sheep and dozens of others in a grisly three-week spate of killings in Somerset.

On Thursday John Chislett, 28, who farms on the Mendip Hills, told how he saw the beast he believes is responsible – a black puma-like animal which calmly stopped to look at him, then disappeared over a hedge.

He said: "The sheep had deep rips in their sides and other injuries which would not have been caused by a dog. Then two days ago when my fiancée and I were up there where the sheep were attacked we saw a big black cat.

"It was like a puma, nothing like a dog. It was just walking down a hedgerow only 30 yards away. It stopped and looked at us and then just carried on walking and jumped over the hedge."

In the past month three farmers who keep sheep in the area have lost dozens of livestock, killed or fatally mutilated by a mystery animal.

Mr Chislett, who lives in the Mendip village of West Cranmore, described his horror at finding animals from his 250-strong flock, dead or dying at Long Cross in Stoke St Michael. Speaking from the scene of the tragedy yesterday he said: "This is no dog. The sheep have slashes across them, deep rips in their sides, their guts have been pulled out and their ears ripped off. Two have had their throats ripped out."

"A dog will chase, worry, kill, and leave, or the sheep often die from the worry of the chase – but this is not the work of a dog."

Four years ago Mr Chislett's father, Ken, 58, experienced similar attacks on his livestock. Not only were sheep killed but a six-month old Aberdeen Angus calf's head was nearly torn off.

"Whether it is the same wild animal or not I don't know, but wild animals can work a large area," said Mr Chislett. There have been reports of sightings of big black puma-like cats north of Wells for several years.

Now Mr Chislett is planning to call in expert shots to try to kill the creature. He is also considering applying for temporary planning permission for a hut so a worker can stay on site and protect the sheep 24 hours a day.

"We have no insurance to cover this sort of thing. It is absolutely heartbreaking to see our prize stock being decimated. We just might as well sell everything up, move away and start again elsewhere," he added.

Farmer Norman Clothier, who farms near Wells, lost six sheep to a dog at Ash Lane, Wells, three weeks ago, and three more were injured with three others having to be put down after a mystery attack at High Littleton. Another farmer lost 10 that were driven into a ditch and drowned.

Norman Clothier's wife, Sylvia said: "Dog owners must keep their animals on a lead when they are walking in a field with sheep. We are entitled to shoot any dog if it worries sheep and hope the public understand. The police are 100 per cent behind us on this."