South Africa's firebrand politician Julius Malema on Wednesday mocked reports that the country's military bases had been put on high alert ahead of his address to soldiers.

"Putting all the camps on high alert ... Since when people gathering to discuss grievances are a security threat in a democratic South Africa?" Malema asked about 30 soldiers who were suspended over an old strike.

The 31-year-old firebrand's plans to address soldiers sparked a warning from Defence Minister Nosiviwe Mapisa-Nqakula that any bid to destabilise the military would be acted on and that troops who attended would be disciplined.

Even though he no longer has any official political role, Malema remains an inflammatory figure in South African discourse and has been playing on frustrations at strike-hit mines after mass shootings by police last month.

The former youth league leader, who was axed by the ruling African National Congress earlier this year, has capitalised on the unrest which has spread to gold mines to push his radical views and attack enemies within the ANC party such as President Jacob Zuma.

"Everything is collapsing, we need to rebuild confidence," he charged in a hall near Johannesburg.

"People don't have roads, clean water, not jobs and those with jobs are treated as slaves. These are the symptom of a dictatorship."

South African National Defence Force (SANDF) spokesman Siphiwe Dlamini told AFP that military bases had been told to monitor the situation, saying he was happy with the media referrals to high alert but that it was "too harsh" a term.

"We have been asking officers to monitor the situation and make sure that everybody is at their work station and reporting to work," he said, adding members of the force should continue with "normal day-to-day duties."

The plight of soldiers suspended in 2009 for a strike over pay is the latest rallying point taken up by Malema, who was booted from the ANC's Youth League this year for ill-discipline and after he was convicted of hate speech.

"Military discipline doesn't mean you must keep quiet when things are going wrong," Malema said.

Of Malema's many comments in recent weeks around the mines crisis, a stand-out remark was his call to make the mining sector "ungovernable".

Mapisa-Nqakula said Malema would not be permitted to make similar calls to the military.

On Tuesday, Malema called for national strikes at all South African mines for five days each month to force mining giants to bow to wage demands.

Forty-five people have died in the strikes since last month, including 34 who were gunned down by police.