At least three explosions have been heard in Harare, the capital of Zimbabwe, with military vehicles also seen on the streets.

Soldiers are also said to have taken over the headquarters of Zimbabwe’s ZBC state broadcaster in the early hours local time, two members of staff and a human rights worker said.

The news comes after Zimbabwe’s ruling party accused the head of the armed forces of treason, as troops took up positions around the capital in a dramatic escalation of a dispute with 93-year-old President Robert Mugabe over political succession.

Just 24 hours after military chief General Constantine Chiwenga threatened to intervene to end a purge of his allies in the Zanu-PF Party, a Reuters reporter saw six armoured personnel carriers on thoroughfares on the outskirts of the capital.

Aggressive soldiers told passing cars to keep moving through the darkness. “Don’t try anything funny. Just go,” one barked at Reuters on Harare Drive.

The presence of troops, including the movement of armoured vehicles from a barracks northwest of Harare earlier in the day, sparked rumours of a coup against Mr Mugabe, although there was no evidence to suggest Zimbabwe’s leader of the last 37 years had been toppled.

Isaac Moyo, Zimbabwe’s ambassador to neighbouring South Africa, dismissed the talk, saying the government in Harare was “intact” and blamed social media for spreading false information.

“There’s nothing really happening. They are just social media claims,” Moyo told Reuters, in Harare’s first official response to the coup rumours.

The southern African nation has been on edge since Monday when General Chiwenga, Commander of the Zimbabwe Defence Forces, said he was prepared to “step in” to end a purge of supporters of sacked vice president Emmerson Mnangagwa.

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Only a few months ago, Mr Mnangagwa, a former security chief nicknamed “The Crocodile”, was favourite to succeed his life-long political patron but was ousted a week ago to pave the way for Mr Mugabe’s 52-year-old wife Grace to succeed him.

The lead item on the ZBC state broadcaster’s news bulletin earlier in the evening was an anti-military rally by the youth wing of Mugabe’s Zanu-PF Party. However, the channel then missed its usual 11pm bulletin, without providing an explanation.

General Chiwenga’s unprecedented statement represented a major escalation of the struggle to succeed Mugabe, the only leader Zimbabwe has known since it gained independence from Britain in 1980.

Mr Mugabe chaired a weekly cabinet meeting in the capital on Tuesday, officials said, and afterwards Zanu-PF said it stood by the “primacy of politics over the gun” and accused Mr Chiwenga of “treasonable conduct ... meant to incite insurrection.”

Army tanks seen heading towards capital Harare, Zimbabwe

The previous day, General Chiwenga had made clear the army’s refusal to accept the removal of Mr Mnangagwa – like the generals, he is a veteran of Zimbabwe’s anti-colonial liberation war – and the presumed accession of Grace, once a secretary in the government typing pool.

Local government minister Saviour Kasukuwere, a leading figure in Grace Mugabe’s relatively youthful ‘G40’ faction, refused to answer Reuters questions about the situation in Harare. “I’m in a meeting,” he said, before hanging up shortly before midnight.

Army, police and government spokesmen refused to answer numerous phone calls asking for comment. State media did not publish the general’s statement. The Herald newspaper posted some of the comments on its Twitter page but deleted them.

The head of Zanu-PF’s youth wing, which openly backs Grace Mugabe, accused the army chief of subverting the constitution.

“Defending the revolution and our leader and president is an ideal we live for and if need be it is a principle we are prepared to die for,” Youth League leader Kudzai Chipanga said at the party’s headquarters in Harare.

Grace Mugabe’s rise has brought her into conflict with the independence-era war veterans, who enjoyed privileged status in Zimbabwe until the last two years when they spearheaded criticism of Mugabe’s handling of the economy.

In the last year, a chronic absence of dollars has led to long queues outside banks and an economic and financial collapse that many fear will rival the meltdown of 2007 to 2008, when inflation topped out at 500 billion per cent.

Imported goods are running out and economists say that, by some measures, inflation is now at 50 per cent a month.

According to a trove of intelligence documents reviewed by Reuters this year, Mr Mnangagwa has been planning to revitalise the economy by bringing back thousands of white farmers kicked off their land nearly two decades ago and patching up relations with the likes of the World Bank and IMF.

Whatever the outcome, analysts said the military would want to present their move as something other than a full-blown coup to avoid criticism from an Africa keen to leave behind the Cold War continental stereotype of generals being the final arbiters of political power.

“A military coup is the nuclear option,” said Alex Magaisa, a UK-based Zimbabwean academic. “A coup would be a very hard sell at home and in the international community. They will want to avoid that.”