Police are linking the killing of three cats in Portsmouth with the "Croydon Cat Killer" believed to be behind 230 deaths in the London area.
A cat was found beheaded in Marmion Road, Southsea, on the night of April 16, with a further two cats found killed within the Hampshire and Isle of Wight area.
One cat was found in Atlanta Close, Southsea, on the night of April 3, and the other in Avenue Road, Sandown, Isle of Wight, on July 22 last year.
A Hampshire Police spokesman said: "We believe these incidents may be linked to Operation Takahe, a series of cat deaths in the Croydon/M25 area, and is being investigated by the Metropolitan Police Service."
Sergeant Tony Jeacock said: "I would like to reassure the public that we are investigating the incident and following all possible leads.
"I would encourage anyone who is aware of any other cats that have been killed, to call 101."
Boudicca Rising, co-founder of South Norwood Animal Rescue and Liberty (Snarl) which has been cataloguing the deaths, said that they had received reports of 230 deaths, 40 of which were foxes, from London and as far afield as Birmingham, Manchester, Brackley in Northamptonshire, and Maidstone in Kent.
She said: "We are very pleased the police are looking at these three deaths."
Ms Rising said that Snarl had investigated the death of the cat on the Isle of Wight, called Fleabags, and added: "From a post mortem it looked whoever had done it had used a different weapon, but we are keeping an eye on it in case the killer was on holiday and didn't have access to their normal toolkit."
Advising London cat-owners to keep their pets indoors at night, she said: "We want people to contact police if they are witnesses, if they don't get anywhere with police please contact us so we can put pressure on them.
"Our advice is not to let cats out at night, most of the deaths are happening at night. If anyone finds bodies please call us and we will come out and get the police out if necessary.
"It doesn't matter where you are in the country, we want to hear about it."
Snarl can be contacted on 07961030064 or 07957830490.
The Metropolitan Police said in June last year that it had already spent 1,020 hours investigating the deaths since the inquiry was launched in December 2015.