South Africa summoned Zimbabwe's high commissioner on Thursday to protest about violent attacks on its businesses in Harare, a senior official said.
It was Pretoria's strongest diplomatic censure so far of the political violence in its northern neighbour.
Top Foreign Ministry official Sipho Pityana told reporters he had met High Commissioner Simon Moyo after receiving calls from South African companies in Harare that had been attacked by militants who called themselves war veterans.
"Our concern is that within this situation South African businesses are entitled to protection," said Pityana, director general at the ministry.
"To that extent we are satisfied by the assurances given to us by the high commissioner on behalf of his government."
South African officials said eight South African companies and their staff had reported being attacked in a stepped-up campaign against businesses in a move to win urban votes for President Robert Mugabe's party.
A number of people had been assaulted, although not seriously, they said. Others had been kidnapped and released after ransom was paid.
South African President Thabo Mbeki has been criticised in Africa and beyond for what some see as his kid-gloves handling of Mugabe's economic and political policies. - Reuters