A £10,000 reward is being offered for information leading to the capture of the so-called Croydon-Cat Killer.
South Norwood Animal Rescue and Liberty (SNARL) has organised the reward money in conjunction with PETA UK and Outpaced.
The killer – also known as the M25-Animal Killer - is also being investigated by the police under the codename Operation Tahake.
Tony Jenkins, co-founder of SNARL, said there have been roughly 220 killings that could have been done by the same person.
The killings are predominantly in south London, but there have also been reports as far as the Isle of White and Manchester.
Mr Jenkins said: “£10,000 is a great sum of money. We hope it will make people vigilant, to look out for anyone acting suspicious.
“These are crimes against humans. The killer places the bodies so they will be found by the owners, they place them where they will be seen.
“Anyone who sees anything should call the police and report it to us.”
Mr Jenkins said publicity is key to support the work a team of SNARL volunteers do to catch the killer.
SNARL was set up in October 2015, but similar cat killings stretch back as far as 2014.
Incidents have been reported all over South London and Kent, including Croydon, Bromley and Dartford.
A spokesman for PETA, which is offering the part of the reward, said: “It’s imperative that any community faced with such sadistic and violent acts take measures to find the culprit and bring him or her to justice.
“Animal abusers are a danger to everyone – they take their issues out on whoever is available to them, human or non-human, and must be caught before they act again.”
Mr Jenkins said public awareness is vital to finding the killer.
He said: “People need to look out for people acting suspicious.
“We advise that owners keep their cats indoors at night and let them out only during the day when they can be supervised. Whilst most of the attacks are happening at night, a handful have happened during the day.”
Anyone with any information should contact the police on 101 and SNARL on 07957 830 490.