Protests forced more than 400 stores of South Africa's biggest pharmacy chain to close on Monday after a controversial "racist" hair advertisement provoked widespread outrage.

Dozens of activists from South Africa's radical leftwing Economic Freedom Fighters (EFF) party picketed outside Clicks Pharmacy stores across the country, forcing them to shut over the adverts posted on the company's website which described black hair as "dull" and white hair as "normal".

South Africa's leading pharmacy, health and beauty retailer, which boasts more than 500 branches across the country, has apologised and pulled down the advertisements.

Clicks said that protests were reported at 425 of its stores, some of which were vandalised, and it was "unable to estimate the total damage to stores given the ongoing protest action."

The federal government said in a statement that while it was disturbed by the "crude racist display" by the advertisement, it called on all South Africans "to resist the temptation to take the law into their own hands."

The advertisements sparked an uproar online, with black women posting images of their afros on Twitter using the hashtags #RacismMustFall and #BlackHairIsNormal.

The South African Human Rights Commission launched an investigation on Monday into the Clicks advert, which it said had "elicited strong emotions and protests from the general public."

The EFF said it wants the retail chain shut for five days.

The protesters want the retail chain shut for five days
The protesters want the retail chain shut for five days AFP / Luca Sola

"They must lose revenue, they must lose profits because of their racism," said EFF vice president Floyd Shivambu, speaking in front of one of the largest stores in Johannesburg's upmarket Sandton business and shopping district -- considered Africa's richest square mile.

He was accompanied by around two dozen chanting supporters.

Further north in Polokwane, the capital of Limpopo province, EFF leader Julius Malema led a group of more than 100 supporters who chanted in front of a shuttered store.

"We are here to say peacefully that racism is violence," said Malema, addressing his supporters at the Mall of the North, the largest in the city.

"We need justice, not apology," said Malema. "Who calls black people ugly?" he asked, calling on the advertising agent to be fired.

"White people insult us and they apologise, they think that is the end," he said.

"We have been projected as ugly people for a very long time by white people. It has got to come to an end at some point and it starts total with Clicks, we are tired."

The EFF condemned all violence, vandalism at its stores and the intimidation of staff and its customers.

The group staged protests in 2018 trashing outlets of Swedish clothing giant Hennes and Mauritz (H&M) in Johannesburg over a controversial advertisement of a black child.

A photo on H&M's website of a black boy wearing a green hoodie with the inscription "coolest monkey in the jungle" triggered outrage on social media.