Killer terrapins are terrorising wildlife at a tranquil Mill Hill pond attacking ducks and ducklings, maiming mallards and battering fish.

Up to 15 of the adult reptiles are believed to be behind a spate of attacks in recent weeks at Sheepwash Pond in The Ridgeway, Mill Hill.

Wildlife experts are warning children not to dip their fingers in the pond as the terrapins have a strong bite capable of severing a finger and could also be carrying diseases such as salmonella.

A spokesman for Barnet Council said it was aware of the problem but did not own or manage the pond. It has, however, produced a fact sheet which says that terrapins can be netted but advised they are best controlled by licensed shooting with a high-powered air rifle.

Children at a playgroup in nearby St Paul's Church are reported to have been left in tears after seeing the terrapins snatch ducklings from their parents and rip the legs off one mallard. Two dead fish, about 1ft long, were also seen in the pond on Thursday (July 29) cause of death unknown.

Liz Barrett, of the London Wildlife Trust Barnet Group, said the full scale of the problem only emerged on July 25 during St Paul's Church's open day when visitors exchanged stories.

"The teachers told us that the children have seen a terrapin attack a duck and bite its legs off. It was very upsetting and they have seen ducklings swimming alongside their mother and disappearing underwater," said Ms Barrett.

"This generally happens with pike in a pond but in this instance it appears to be the terrapins. If you think about it, these things have got to eat and there is little other food in there for them."

The reptiles are red-eared terrapins of either Italian, Spanish or North American origin which are similar in colour to a tortoise.

Terrapins were bought as pets during the Teenage Mutant Ninja Turtles craze in the early Nineties but illegally released into ponds and lakes when children got bored of them.

Ms Barrett added: "Certainly if a child is sitting quietly and dipping their hand into the pond then little fingers could make a tasty meal for the terrapins. They can be quite dangerous as well as rather endearing."

A council spokesman said: "We would support London Wildlife Trust's suggestion of producing a management plan that focuses the efforts of the volunteers."