Police are investigating reports that urban foxes are being caught in London then used as bait for fighting dogs.
Gangs with dogs and nets have been spotted hunting in woodland in the Rotherhithe area of the capital.
Two dead foxes have been found and three dead cats have also been discovered "ripped to pieces."
Wildlife campaigners believe the foxes are caught and used as bait for dogs ahead of illegal fights.
Posters have been nailed to trees in the Russia Dock Woodlandpark in Rotherhithe warning of the problem.
Members of The Friends of Russia Dock Woodlandand the Trust For Urban Ecology (TRUE) met with local council members and residents at an emergency meeting this week.
Police have launched an investigation.
Rebeka Clark from TRUE, which has a base at the park, said dog walkers had reported seeing gangs going into the woods at night.
Others have been spotted at an old football stadium in the area where foxes are known to live in the base of the stand.
"I believe people are killing or stealing the foxes which are then used as bait for dogs," Clark said. "Two young foxes have been found dead without injury or disease which suggests they have died of shock from being chased or held.
"Three cats have also been found completely ripped to pieces. The matter has been referred to the police."
Steve Cornish, chairman of The Friends of Russia Dock Woodland, said he understood that gangs were catching the foxes and using them to bait dogs.
"We have had reports that the foxes are thrown in with the dogs to get them into a frenzy, to keep them in a fighting state ahead of bouts.
"Gangs have been spotted by the football stadium with nets, trapping the animals and taking them away."
Southwark's wildlife crime officer Pc Mark Wood said police were investigating the reports.