Zimbabwe's President Robert Mugabe has fired Emmerson Mnangagwa as vice president after he showed "traits of disloyalty", his information minister said on Monday, removing a favourite to succeed the 93-year-old leader.

Mnangagwa's removal provides a boost for Mugabe's wife, Grace, who has been a vocal critic of the vice president and is also seen as a potential successor to her husband.

"The vice president has consistently and persistently exhibited traits of disloyalty, disrespect, deceitfulness and unreliability," minister Simon Khaya Moyo told reporters.

"It had become evident that his conduct in his discharge of his duties had become inconsistent with his official responsibilities."

Neither Mnangagwa nor his aides could immediately be reached for comment.

Grace, 52, called Mnangagwa a coup plotter and a coward on Sunday in a speech that inflamed an already bad-tempered rift in the ruling Zanu-PF party.

It followed a speech by Mugabe at a rally on Saturday where he publicly rebuked his deputy for the first time.