A shepherd believes his flock of sheep is being deliberately targeted by a dog walker letting their animal off its leash, after seven were killed within the last fortnight.

Two weeks ago the Bucks Free Press reported a ewe at Bowstridge Farm, Chalfont St Giles, was mauled to death and another had to be put down after being attacked by a dog.

Since then two more ewes and five lambs have all been killed by a dog - with one of the ewes being bitten in the face.

Police have since increased patrols in the area to try and catch the culprit but Matt Whiles, the shepherd who tends to the flock, is concerned at the impact the attacks are having on the business.

He said: "It's our turnout land. We've got another flock of nearly 500 ewes due to lamb over the next two weeks - that's the only place we've got to put them.

"It's a huge worry and we are looking for other land to rent. It has a huge impact on the business.

"I've been told a chap has been seen letting the dog off the lead to chase the sheep deliberately.

"It's been reported to the police and they are coming down three times a day. From a practical point of view, we'd check them first thing in the morning, feed them and leave. Now we are going three times a day ourselves. It's having a huge impact on us. It's still happening with a great regularity."

Mr Whiles said after the first two attacks he put up signs on gates surrounding the farmland requesting dog owners keep their pets on leads, but all bar one of them were instantly ripped down again.

Thames Valley Police said in a statement: "All dog owners are reminded that it is against the law to let a dog be dangerously out of control in a public place.

"When out walking your dog on public footpaths that run through private land, please ensure your dog(s) are under proper control and remain within the public area.

"Please keep dogs away from sheep and other farm animals and under proper control and do not allow them to worry the animals."

Anyone with information about the incidents can contact police on 101, or the Crimestoppers charity anonymously on 0800 555 111.