The ZANU-PF party criticised General Constantino Chiwenga who had demanded that Mugabe stop purges of senior party figures, including Vice president Emmerson Mnangagwa who was dismissed last week.
The military spokesman was not available to comment.
Mnangagwa had always been tipped as Mugabe's most likely successor but has in recent months increasingly come into conflict with first lady Grace Mugabe, who is vying to replace the 93-year-old president. Whilst reports on social media seem to imply that a coup is underway, Khuluma Afrika understands that military presence has been increased there to improve security in the face of growing uncertainty in the country.
eNCA's Zimbabwean correspondent Pindai Dube confirmed the tanks were visible in the streets of Harare, with sources indicating it was a "show of force" rather than a coup.
"Chiwenga threw down the gauntlet to Mugabe.it would make sense for Chiwenga to organise some military manoeuvres to up the ante".
His lengthy rule has been marked by brutal repression of dissent, mass emigration, vote-rigging and economic collapse since land reforms in 2000.
"No one wants to see a coup".
In a rare statement that highlighted the tensions rising in the impoverished southern African nation, General Constantino Chiwenga, commander of Zimbabwe Defence Forces said there was instability in ZANU-PF, which was causing anxiety in Zimbabwe. The long-serving veteran of Zimbabwe's 1970s liberation war, had been viewed as a likely successor to Mugabe before the president fired him.
He fled the country and is thought to be in South Africa after issuing a searing five-page condemnation of Grace's ambition and Mugabe's leadership.
Chiwenga's statement, read out at a news conference packed with army top brass, comes at a time of a deepening rift within ZANU-PF over who will eventually lead the party after the 93-year-old Mugabe goes.
Earlier this year the country was gripped by a freakish spat between Grace and Mnangagwa that included an alleged ice-cream poisoning incident that laid bare the pair's rivalry.
President Robert Mugabe with his wife Grace Mugabe.
Grace, now poised to become a vice president, did not fight in the liberation war.