The 25-year-old was campaigning in the area when the incident happened.
Passerby Andries Mashabane (61) was also attacked by the dogs.
ANC regional spokesman in the Waterberg, Matome Tauatsoala, accused the dog owner of intentionally opening the gate so dogs could attack the volunteers.
“This is a case of political intolerance and we can’t rule out racism,” he said.
“We condemn with strongest possible terms the behaviour of a white man in Mokopane who opened the gate for two pit bulls to attack an ANC volunteer.”
Tauatsoala said the volunteers were placing ANC posters around the area.
“The dogs also attacked a passerby.”
He said they had to go to the casualty ward in hospital but the dogs’ owner denied opening the gate.
“The ANC will raise this with the IEC. When our volunteer was being attacked by the dogs, the owner was sitting under the tree without making any effort to restrain his animals,” Tauatsoala said.
Sema told the reporter he tried to protect himself but together the dogs overpowered him.
“Now my hand is hurt and it doesn’t work properly,” he said.
“I was discharged by the hospital doctor but I might go to a private doctor because the pain is unbearable.
“I opened a case against the owner at Mokopane Police Station,” he said.
Limpopo police spokesman Brigadier Motlafela Mojapelo said: “We can confirm that an assault case was opened after two dogs attacked a 25-year-old victim on Wednesday.”
Police are investigating.