FARMS across North Cornwall will need to become like "Fort Knox" in order to deter organised gangs from sheep rustling, concerned farmers have claimed.

In the latest incident 33 Scotch mule ewes were stolen from a Week St Mary farm, a month after a Davidstow farmer lost 42 ewes in lamb and five rams from a field at Advent.

Phil Parsons, a cattle and sheep farmer from South Petherwin, said farmers across North Cornwall are now on high alert. "There has always been a history of sheep rustling but what's going on now appears to be on a very organised scale. These people are knowledgeable and well geared up," he said.

"It is a big concern to all farmers. There's a sense of vulnerability but you cannot put security fences all around the cattle and sheep. It sometimes feels like we have to turn our farms into Fort Knox.

"This will be yet another cost to farmers and another worry."

Sheep rustling is on the increase across the country, with lamb at its highest price yet.

Police are urging farmers to be extra vigilant and ensure that gates are not only padlocked but that the hinges are secured too.

The police and the NFU believe the rustlers are highly organised because of the logistical difficulties in stealing, moving and disposing of large numbers of sheep.

A spokesman for the NFU South West region said: "I am aware that we are getting more reports of this right across the country. I know of 100 sheep being taken from a place just outside Exeter. The thing about this kind of theft is that you have to be pretty well organised to carry it out. You have to be able to round the sheep up, have a means of moving them and somewhere to take them. We're looking at a highly mobilised and highly organised operation. There is a huge rise in demand currently for certain types of lamb and sheep prices are flying."

He added: "Theft like this is a substantial blow to a farmer. Farmers adhere to strict animal welfare regulations, taking good care of their stock and are responsible for all sorts of DEFRA requirements so that all meat is traceable. But the people committing this sort of crime have scant regard for animal welfare or the regulations. We would advise all farmers to take part in some type of local initiative such as farm watch and to put locks on all gates and hinge ends.

"The harder it is to steal your stock, the less likely you are to be a victim.

"There do seem to be signs that the police are looking more at rural crimes and I hope they will be looking at this very seriously.

"Farmers and people whose property adjoins farmland should be vigilant.

"Report anything that seems unusual and note down number plates if you see people hanging around."