The Zimbabwean military has seized control of the capital Harare and state media, and has President Robert Mugabe confined to his home.

Key points: Tanks and troops are seen taking positions around capital Harare

Tanks and troops are seen taking positions around capital Harare The ruling party says that it will never succumb to army threats

The ruling party says that it will never succumb to army threats Army chief threatened to intervene in politics earlier this week

In a televised statement, Zimbabwe's army denied it was mounting a military takeover, insisting that Mr Mugabe and his family were safe.

South Africa's President Jacob Zuma said he spoke to Mr Mugabe, who told him that he was confined to his home but was fine, the South African presidency said in a statement.

The presidency added that Mr Zuma, in his capacity as chair of the Southern African Development Community, was sending special envoys to Zimbabwe to meet with Mr Mugabe and the Zimbabwean Defence Force.

The security of the 93-year-old President and his wife "is guaranteed", the army said.

"We are only targeting criminals around [Mugabe] who are committing crimes that are causing social and economic suffering in the country in order to bring them to justice."

The statement broadcast on the state-run Zimbabwe Broadcasting Corporation came after a night of unrest, during which armoured vehicles took to the streets and explosions were heard in the capital Harare.

Soldiers had earlier taken over the headquarters of the state broadcaster, compounding speculation of a military coup against Mr Mugabe.

A government source said the military also detained Finance Minister Ignatius Chombo, a leading member of the so-called "G40" faction of the ruling ZANU-PF party.

The faction, led by Mr Mugabe's wife Grace, had been vying to succeed the 93-year-old President.

Zimbabwe's ruling party had earlier accused the head of the armed forces of treason, escalating the rupture between Mr Mugabe and the military's top brass.

Soldiers blocked the road leading to Mr Mugabe's office. ( AP: Tsvangirayi Mukwazhi )

The events came less than 24 hours after military chief General Constantino Chiwenga threatened to intervene to end a government purge in the ruling party.

"We are deeply concerned by reports out of Harare, we are in contact with our High Commission and are monitoring situation closely," Australia's Foreign Minister Julie Bishop said.

"Zimbabwe has a volatile history, I recall being an electoral observer there in 2002.

"It's deeply distressing to hear that the political situation is again as volatile as it appears."

In response to the escalating domestic political tensions and unpredictable security situation in Zimbabwe, Australia's Department of Foreign Affairs and Trade updated its travel advice for Zimbabwe on its official Smartraveller website.

A street scene along Robert Mugabe road in Harare. ( AP: Tsvangirayi Mukwazhi) )

Australians in Zimbabwe are advised to reconsider their need to travel to Harare, remain indoors and be aware of their surroundings.

They should also avoid large gatherings or protests, and monitor the media and other information sources.

"We are in contact with the High Commission in Harare to make sure everyone is safe," Ms Bishop said.

"If any Australians have concerns about family or loved ones in Zimbabwe they should contact the DFAT hotline," she said.

'Treasonable conduct to incite insurrection'

Robert Mugabe has been in power for all 37 years of Zimbabwe's independence. ( AP: Tsvangirayi Mukwazhi )

The Southern African nation has been on edge since Monday, when armed forces chief Constantino Chiwenga openly threatened to intervene in politics, a week after Mr Mugabe fired vice-president Emerson Mnangagwa, long seen as 93-year-old Mr Mugabe's likely successor.

Former VP Emerson Mnangagwa (right) was removed from office last week amid attacks from Grace Mugabe (left). ( Reuters: Philimon Bulawayo, file )

"We must remind those behind the current treacherous shenanigans that, when it comes to matters of protecting our revolution, the military will not hesitate to step in," General Chiwenga said in a statement read to reporters at a news conference packed with top brass on Monday.

Mr Mnangagwa, a veteran of Zimbabwe's 1970s liberation wars, was popular with the military, which viewed his removal as part of a purge of independence-era figures to pave the way for Mr Mugabe to hand power to his wife Grace, 52.

On Tuesday, Mr Mugabe, the only leader Zimbabwe has known in 37 years of independence, was chairing a weekly cabinet meeting in the capital.

But shortly after reports of tanks nearing the capital came through, Zimbabwe's ruling ZANU-PF party released a statement saying it would never succumb to military pressure.

In the statement, the ruling party said it stood by the "primacy of politics over the gun" and accused General Chiwenga of "treasonable conduct … meant to incite insurrection".

'Rupture between Mugabe and armed forces'

General Chiwenga addresses a press conference in Harare. ( AP: Tsvangirayi Mukwazhi, file )

Ms Mugabe had long-developed a strong following in the powerful youth wing of the ruling party.

But her rise has brought her into conflict with the independence-era war veterans, who once enjoyed a privileged role in the ruling party under Mr Mugabe, but who have increasingly been banished from senior government and party roles in recent years.

The rising political tension in the southern African country comes at a time when it is struggling to pay for imports due to a dollar crunch, which has also caused acute cash shortages.

Martin Rupiya, an expert on Zimbabwe military affairs, said the army appeared to be moving to put the squeeze on Mr Mugabe.

"There's a rupture between the executive and the armed forces," Mr Rupiya said.

ABC/Wires