Johannesburg - The NSPCA is investigating an apparent dog fighting event which was advertised on a website and mobile billboard in Johannesburg on Monday.
Pictures of the billboard went viral on social media sites, prompting people to inundate the NSPCA with reports.
Spokesperson Wendy Wilson said she had been overwhelmed with reports of the billboard, which she described as "brazen".
"We have been inundated with calls about this this morning and we are investigating now," she said.
"This is something that we are very used to and I don't think that the general public is used to seeing something so brazen," Wilson added.
She confirmed that dog fighting in any form was illegal.
"It is 100% illegal and everything to do with it is illegal. The dog fighting scene is huge and it has grown rapidly over the years and seems to be becoming South Africa's national sport," she said.
"There is a lot of money to be made out of this blood sport," she added.
Calls to the number listed on the billboard go directly to a booking line voicemail.
@mali_ghana Thanks for contacting us. Our Special Investigations Unit is investigating.
— NSPCA South Africa (@NSPCA_SA) June 27, 2016
Tell me this is not legit! Surely this is not legal and should not be in ANY country!! @SAPoliceService @CICArsa pic.twitter.com/oK4Y8l8pSs
— PigSpotter Cliff (@PigSpotter) June 27, 2016