Zimbabwean President Robert Mugabe openly pilloried his deputy and possible successor Saturday, saying he might sack him, in a combative speech at a rally where his wife Grace was booed by some in the crowd.

The 93-year-old leader's remarks exposed tensions in the ruling ZANU-PF party over who stands to take power after him, an event only expected when Mugabe dies but a generational change likely to prompt bitter battles.

Vice President Emmerson Mnangagwa, nicknamed "the Crocodile", is one of the top candidates.

But Grace Mugabe -- 41 years younger than her husband -- has become increasingly active in public life in what many say is a political grooming process to help her eventually take the top job.

Mnangagwa has been accused by Mugabe loyalists of undermining the president and of fanning factionalism in ZANU-PF, which has already named the incumbent as its candidate for next year's presidential election.

Mnangagwa, 75, was appointed vice-president in 2014 and has been widely touted as the obvious successor to Mugabe, who has led the country for 37 years.

But a visibly incensed Mugabe unleashed wrath at his vice-president, sitting nearby, when speaking in Shona in the opposition stronghold city of Bulawayo.

"We are denigrated and insulted in the name of Mnangagwa. Did I make a mistake in appointing him as my deputy?" Mugabe asked.

- 'You know nothing' -

"If I made a mistake by appointing Mnangagwa... tell me. I will drop him as early as tomorrow. We are not afraid of anyone. We can decide even here," he said.

"If it has come to this, it is time we make a final decision," he added, telling Mnangagwa and his supporters they were free to leave ZANU-PF.

"You can go ahead and form your party because we honestly cannot have this. We cannot be insulted on a daily basis."

Some rallygoers heckled Grace Mugabe, chanting at her "you know nothing" and "you are too junior" as the first lady spoke before a section of the crowd that broke into a popular local song "oyenzayo siyaizonda" which translates to "we hate what you do."

She shouted back at the hecklers: "If you have been paid to boo me, boo, go ahead...I don't care, I am powerful."

She then repeated her ambition to be appointed her husband's deputy.

"Even if I become vice president, is there anything wrong with that?"

Mnangagwa was last month stripped of his role as justice minister, in a cabinet reshuffle widely considered part of a campaign to reduce his powers and quash opposition within the government.

Source: AFP