Military bases in South Africa have been placed on high alert for the first time since the advent of democracy in 1994, defence officials have confirmed.
The move comes as firebrand politician, Julius Malema prepares to address disgruntled soldiers near Johannesburg.
The defence minister accused him of trying to "mobilise against the state".
Malema has addressed several rallies in recent weeks, demanding President Jacob Zuma's removal from power after police shot dead striking miners.
Defence department spokesman, Sonwabo Mbananga told the BBC that all bases were on high alert to "keep vigilance over the movement of our armed forces".
It is an extraordinary move, all because Malema is due to address some soldiers, the BBC's Andrew Harding reports from Johannesburg.
Malema was expelled from the ruling African National Congress (ANC) party in April, and is under investigation for alleged corruption.
But Malema has seized on the killings at the Marikana platinum mine last month - when police shot dead 34 protesting workers - to launch a ferocious campaign against South Africa's elites, and to call for an economic revolution, our reporter says.
The army's shrill reaction to his latest move underlines Malema's apparent power, he adds.
Malema's spokesman, Floyd Shivambu said Malema planned to meet soldiers near a military base in the Johannesburg area.
"The meeting is as a result of the pleas and requests the armed forces, soldiers of the SANDF [South African National Defence Force], sent to Malema to come listen to and voice the military and soldiers' cries and demands," Shivambu said.
Defence Minister Nosiviwe Mapisa-Nqakula accused Malema of trying to "mobilise against the state" and "agitating people to become ungovernable".
"It cannot be allowed to happen in the SANDF," she said.
Johannesburg-based political analyst William Gumede argues that Malema is similar to politicians in Zimbabwe's Zanu-PF party, led by President Robert Mugabe.
South Africa is in a jittery mood right now, partly because of fears that labour unrest could spread, and partly because the government appears preoccupied with infighting, as factions plot ways to unseat President Zuma, our correspondent says.
On Wednesday, Malema called for a national strike in the mining sector, South Africa's economic backbone.
Police spokesman Thulani Ngubane said on Thursday that workers at a platinum mine in North West province, owned by the world's top platinum producer, Anglo American Platinum (Amplats), have launched a strike, AFP news agency reports.
"They are rioting, barricading the roads with tyres, trees trunks and rocks," Ngubane is quoted as saying.
Amplats spokesman, Mpumi Sithole told the BBC the protesters were not employees of the company.
"Our employees have been moved to a neutral place away from the mine. Some operations are not operating," Reuters news agency quotes Ms Sithole as saying.
The conflict has led to a fall in the price of Amplats shares.
Malema has been touring mines since the Marikana killings, rallying support against the government, its trade union ally, the National Union of Mineworkers (NUM) and big business.
"They have been stealing this gold from you," Malema told cheering miners on strike at a gold mine west of Johannesburg on Wednesday, "now it's your turn."
Ms Mapisa-Nqakula said the government could not allow an "ordinary citizen" to "instigate and agitate" on mines, and to now turn his attention on the SANDF.
"It is unacceptable. It is wrong...They are all indications that this is counter-revolutionary," she said.
Malema is currently being investigated over alleged corruption related to government tenders in South Africa's Limpopo province, his political stronghold.
He denies any wrongdoing.
He was expelled from the ANC following a series of disagreements with Zuma.
He is lobbying ANC members to vote Zuma out of power in party elections due in December - a move that could trigger the downfall of Zuma's government, our correspondents say.