On Tuesday, the ANC called AfriForum Youth "irrelevant" and "isolated", following Monday's event.
AfriForum Youth said the event celebrated the lives of 19 people killed in the 1983 Church Street bombings. AfriForum Youth's national president Charl Oberholzer said the ANC tried to rewrite history by portraying its leaders as heroes.
"Thousands of innocent civilians, black and white, paid a terrible price during these violent attacks by the ANC. The event is not only a protest against the ANC's biased rewriting of history in which ANC leaders are portrayed as blameless heroes, but also an opportunity to celebrate the lives of those who died in terror attacks," Oberholzer said.
He said the ANC's "dark history" was often "glossed over".
"But the reality is that many families are still struggling to cope with the brutal way in which their families were murdered," said Oberholzer.
"More than 500 people were killed by means of necklacing since 1984, hundreds were set alight while still alive and 250 were killed in bomb or landmine attacks by the ANC. Even though the ANC did sign the Geneva Convention in 1980 and undertook not to target ordinary South Africans, 80% of terror attacks by the ANC targeted innocent civilians," he added.
ANC spokesperson, Keith Khoza, said AfriForum's views were "unfortunate", and said the ANC was not aware of the event.
He said it was necessary for the ANC to rewrite it's history to some extent, because it had been distorted during apartheid.
But, he said, history had to be factual and based in reality. Khoza added the party encouraged people – "even white people" – to start documenting their own history, whether it occurred pre- or post-1994.
He said AfriForum's decision to call the ANC "terrorists" was unfortunate, and said the organisation was constantly wanting to "go back to the past".
"We know that AfriForum represents the past; they are not forward-looking and, unfortunately, the progression of time is not working in their favour.