Criminals are scouting Melbourne suburbs for pets to steal and use in illegal dog fights, according to social media.

A Facebook post, which has been shared more than 5000 times in just over a week, displays a picture of a piece of plastic nailed to a tree and claims it is a “dog fight marker” placed on Settlement Road, Bundoora in Melbourne’s north.

Liana Horn, who posted the image on January 27, said the markers “indicate a dog to be either used for bait or for a dog fight”.

“Please look out for these and keep your eyes peeled,” she wrote.

“Police have been alerted…. be on the look out on fences, trees and power lines as I didn’t think that these things would happen to me.

“Please share as much as you can with all dog owners.”

Ms Horn, who owns a staghound crossbreed, had previously been told by three people that dog fight markers exist.

“I knew it was dog tagging because I was warned by my vet, the adoption place I got my dog off of and one of my friends who had researched into it,” she said.

“Also, one of my work friends has two pitbulls and this has been happening to him for four years now.

“He said that the tag was the same as the ones they used on his property.”

Ms Horn said she has resorted to installing security cameras on her property out of fear her dog may be taken.

Victoria Police said it had no information on dog fight markers and could therefore not verify the accuracy of Ms Horn’s claims.

“I can’t confirm if it is a hoax or not as we know nothing about them as far as I can determine,” Inspector Ian Geddes said.

The post has evoked impassioned responses from dog lovers and continues to be shared at a rapid rate.

“You know that’s the third status about this exact thing I’ve seen tonight? I wonder if they do it in waves or something,” one comment states.

Another claims the dog fight markers are appearing in other areas of Melbourne.

“They are doing it in Melton and Bacchus Marsh as well,” the comment states.

RSPCA Victoria Inspectorate Manager Allie Jalbert could not confirm if markers were being used to identify homes with dogs.

“We do hear anecdotally of dog fights occurring in Victoria, but the activity is very difficult to detect,” Mr Jalbert said.

“RSPCA Victoria works closely with Victoria Police to investigate any information or reports that come to light regarding illegal dog fighting activity.”

In July last year, a Melton woman claimed her dog was stolen and used as a ‘‘bait dog’’ for illegal dog fighting.