President Jacob Zuma on Thursday expressed concern about what he termed a "culture of extremity" in South Africa and warned striking workers and other protesters to respect the law.

"The extreme manner in which some of our citizens tend to express their grievances lately is totally unacceptable," the president told a media briefing at Tuynhuys.

"We are concerned about the culture of extremity in everything. What would in other countries be petty crime, in our country becomes violent crime as some people kill even for a cellular phone.

"There is something seriously wrong with such conduct."

Zuma condemned the violent salary protest by soldiers at the Union Buildings last month as "despicable in the extreme" and warned other citizens to express their grievances in a peaceful manner.

"We cannot continue to loot shops, burn tyres, throw garbage on our streets, blockade roads, damage property or most disturbingly, march in violation of court orders to voice your dissatisfaction."

Zuma said the government had ordered the police to deal "harshly and firmly" with anybody who broke the law.

The president in July rejected notions that a spate of sometimes violent service delivery protests since he took office in autumn was a sign of increasing civil unrest in the country.

He has acknowledged that many protesters had valid grievances and that some of these were caused by the ANC's failure to function properly at local government level.