The RSPCA said the animals had been mutilated before being killed.

A motorist found the fish tank at Lower Condurrow Road near Camborne.

The RSPCA said a vet who examined the animals found they had suffered a variety of injuries including broken backs, ribs, legs and puncture wounds.

An inquiry has been launched and one of the charity's inspectors, Mike Reid, said there was no doubt they had been killed deliberately.

He said the white rats, mostly adults, probably belonged to someone who was having difficulty in coping with their numbers or in finding them homes.

They want to hear from anyone who may have been offered a pet rat or knows anyone who breeds rats for sale.