Zimbabwe is on edge after armoured personnel carriers were seen outside the capital a day after the army commander threatened to “step in” to calm political tensions over the president’s firing of his deputy.

The Associated Press saw three armoured personnel carriers with several soldiers in a convoy on a road heading toward an army barracks just outside the capital Harare.

While it is routine for armoured personnel carriers to move along the route, the timing heightened unease that there is an open rift between the military and 93-year-old President Robert Mugabe.

Zimbabwe's army commander Constantino Chiwenga has criticised the instability in the country’s ruling party (Tsvangirayi Mukwazhi/AP)Zimbabwe’s army commander Constantino Chiwenga had threatened to “step in” to calm political tensions (Tsvangirayi Mukwazhi/AP)

The military has been a key pillar of Mr Mugabe’s power since independence from white minority rule in 1980.

Mr Mugabe last week fired vice president Emmerson Mnangagwa and accused him of plotting to take power, including through witchcraft.

Mr Mnangagwa, who enjoyed the backing of the military and was once seen as a potential successor to Mugabe, fled the country and said he and his family had been threatened.

More than 100 senior officials allegedly supporting him have been listed for disciplinary measures by a faction associated with Mr Mugabe’s wife Grace.

The first lady, whose political profile has risen in the past few years, now appears positioned to replace Mr Mnangagwa, leading many in Zimbabwe to suspect that she could succeed her husband as president.

On Monday, army commander Constantino Chiwenga issued an unprecedented statement saying purges against senior ruling ZANU-PF party officials linked to the 1970s liberation war should end “forthwith”.

“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,” the army commander said.

Mr Mugabe did not respond to the military statement and government spokesman Simon Khaya Moyo said only the president could respond. The state-run broadcaster did not report on the statement.

The ruling party’s youth league, aligned to the first lady, on Tuesday criticised the army commander’s statement, saying youth were “ready to die for Mugabe”.

State broadcaster Zimbabwe Broadcasting Corporation was operating as usual and the capital remained calm.