The ruling party condemned what "appeared to be an attempt to burn down its headquarters, Chief Albert Luthuli House", in Johannesburg, at around 6pm on Tuesday, it said.
According to spokesperson Jackson Mthembu, "A suspicious fire broke out at the reception of the building next to the main entrance. The suspicious fire burned a reception couch and damaged glass.
"We view this in serious light as it appears as an act of attempting to destabilise the ANC through acts of arson and sabotage."
The fire was doused when the headquarter's security personnel used fire extinguishers to douse the flames "that were almost reaching the ceiling of the reception area", said Jackson.
"The police have taken over the parameters of Luthuli House with a view to investigate the source the fire and to ensure that there is no other pending threat to the building and people in the building," he said.
Neither the police nor the Johannesburg emergency services could confirm the incident.