Zimbabwe President Robert Mugabe’s grip on power is looking increasingly tenuous as a dispute with the country’s armed forces escalates with troops taking up positions around the capital.

The African nation’s ruling party has accused General Constantino Chiwenga of treason as the armed forces dispute with 93-year-old Mr Mugabe escalates over political succession.

Just 24 hours after military chief General Chiwenga threatened to intervene to end a purge in the ruling party, a Reuters reporter saw six armoured personnel carriers Tuesday local time on major thoroughfares on the outskirts of the capital.

Aggressive soldiers directing traffic told passing cars to keep moving through the darkness.

“Don’t try anything funny. Just go,” one soldier said on Harare Drive.

The presence of troops sparked rumours of a coup against Mugabe, although there was no evidence to suggest Zimbabwe’s leader of the last 37 years had been toppled.

The country has been on edge since Monday when Chiwenga said he was prepared to “step in” to end a purge of supporters of a sacked vice president.

The unprecedented statement represents a tussle over who will succeed Mugabe, who has been in power since the country gained independence from Britain in 1980.

Mugabe’s ZANU-PF said it stood by the “primacy of politics over the gun” and accused Chiwenga of “treasonable conduct… meant to incite insurrection.”

Mugabe fired Vice President Emerson Mnangagwa last week.

The veteran of the 1970s liberation war was popular with the military and had been seen as a likely successor to Mugabe.

The army views his removal as part of a purge of independence-era figures to pave the way for Mugabe to hand power to his wife Grace Mugabe.

A Reuters witness saw two armoured vehicles parked beside the main road from Harare to Chinhoyi, about 20 km from the city.

Witnesses said they saw four armoured vehicles turn before reaching Harare and head towards the Presidential Guard compound in a suburb on the outskirts of Harare.

“There were about four tanks and they turned right here, you can see markings on the road,” one witness on the Chinhoyi highway said, referring to the armoured vehicles.

– With AAP