A dog owner whose pet has gone missing from her Oxford garden claims animal rights protesters may have stolen it.

Caroline Howkins said Black Labrador Charlie was dognapped on Wednesday from the shed he was kept in at their South Hinksey home.

She had previously received three letters claiming to be from animal rights activists, demanding the pet was allowed out of its pen or they would "take action".

A month before the break-in, two suspected animal rights protesters were scared off after breaking a fence and trying to reach the dog in the back garden.

Now Mrs Howkins and her husband Peter are pleading to the thieves to return the family pet, and have asked police to track down the suspected protesters.

She said: "We had a little bit of a problem beforehand with Charlie when some people came round and broke the fence. Now we're worried about where he is and how he is."

Charlie went missing between 5.30pm and 6.30pm on Wednesday, when the family were out of the house.

His owners have denied accusations that the dog was mistreated, and said he was not kept inside the pen all the time, but was taken on daily walks and allowed to roam free in the back garden.

Mr Howkins said: "Charlie has a very easy temperament and is a very good dog, but slightly on the heavy side and very strong.

"I wouldn't mind if I knew the dog was with another family and happy, then they could have him if he was well looked after -- but it's difficult because we don't know."

The family, who own four more dogs, had been sent three letters warning that protesters would take Charlie away. One letter threatened: "We notice your dog is still being locked up 23 hours out of 24. We intend to take action if this situation does not change.

"We will be informing the general public of how you are treating your dog.

"There will be many people who will be distressed at how your dog is treated."

None of the letters were signed, but all were written on Animal Liberation Front paper. They have now been handed over to police.

Since the theft, the couple have been searching Oxford into the early hours of the morning for traces of the pet.

Four weeks ago, Mr Howkins saw two women, one dressed with a white coat pulled up around her face and a second dressed in black, trying to break into the pen, but they disappeared when Charlie started barking.

The RSPCA was called out but tests revealed Charlie was unharmed and fit and healthy.

A police spokesman said: "Police are investigating reports of the stolen dog but all avenues are being investigated and it is still very much an open investigation."

The Animal Liberation Front was not available to comment.

The couple do not want to reveal their address but anyone with information on Charlie's whereabouts should call Oxford police on 08458 505505.