Mantashe said the ANC was going through a stressful period and needed to unite.
He told Ekurhuleni mayor Mondli Gungubele to consider honouring the deceased.
"I hope as we commemorate Chris Hani every year we will also find space to commemorate these combatants.
"We should use their death to unite the ANC. Comrades must use this occasion to unite the movement," he said.
Mantashe told mourners not to lose hope as the government would ultimately deliver on its promises.
He said the opposition parties were trying to confuse communities by creating an impression that the ANC had failed to deliver.
ANC Youth League president Collen Maine said mourners should vote for the ruling party in honour of those who died.
ANC Ekurhuleni chairman Mzwandile Masina said the deceased were committed ANC volunteers who attended the manifesto launch in Port Elizabeth as part of serving their communities.
"They paid the highest price, with their own lives.
"In respect of the price they paid we should make sure that the ANC retains power in our region," Masina said.