Cabinet on Thursday warned of stronger police action against the organisers and those taking part in violent and destructive protests.

"Those who organise these marches, those who openly perpetuate and promote violent action, the State will start acting against those individuals," government spokesperson Themba Maseko told a media briefing in Cape Town, following Cabinet's fortnightly meeting on Wednesday.

The warning comes a day after rampaging soldiers invaded the grounds of the Union Buildings in Pretoria, damaging vehicles and throwing a petrol bomb, before being dispersed by police using rubber bullets and teargas.

Maseko said the Cabinet condemned, "in the strongest possible terms", the illegal and violent protest at the Union Buildings by members of the South African National Defence Union.

Among other things, it had caused untold damage to South Africa's reputation as a stable and emerging democracy.

"Defying a court order, engaging in unnecessary violent behaviour, causing damage to private and public property, and attempting to invade the seat of government is totally unacceptable.

"The time is fast approaching where the State cannot be expected to stand by while the laws of the land are being trampled upon."

Asked to spell out what new, stronger action might be taken against such violent protests, Maseko said the police would be "mandated to make sure that there is strict compliance with the laws of the land".

Several soldiers and a policemen were injured, and police and military vehicles were damaged on Wednesday, when the protest by 3 000 soldiers demanding higher wages turned violent.

Two soldiers were arrested.

Defence Minister Lindiwe Sisulu angrily described the incident as "anarchy" and said it had put national security at risk.

Maseko said those who actively participated in burning and destroying property, both public and private, must expect to be arrested by the police.

"Not enough of that has been happening, and you should expect to see a stronger hand on the part of the police to actually make sure that people are held to account for breaking the laws of this country," he said.