Zimbabwean President Robert Mugabe on Monday fired a vice-president who had previously been seen as a likely successor, removing an obstacle to the presidential ambitions of Mugabe's wife.

Vice-President Emmerson Mnangagwa was removed from office "with immediate effect," the government said, opening the way to the possible appointment of Grace Mugabe to the post.

The 93-year-old president and his wife have in recent months accused Mnangagwa of plotting to oust Zimbabwe's leader, who has been in power since independence from white minority rule in 1980.

Mnangagwa had been vice-president since 2014 when his predecessor, Joice Mujuru, was fired for allegedly plotting to oust Mugabe. His dismissal was announced by Simon Khaya Moyo, the information minister.

Mnangagwa was the most prominent of two vice-presidents and had been part of Mugabe's cabinet since independence in 1980. He is said to have enjoyed the support of military generals and war veterans; his critics view him as ruthless because he was in charge of state security when Mugabe unleashed a North Korean-trained brigade to crush dissent in western Zimbabwe in the 1980s.

Zimbabwe Politics

Emmerson Mnangagwa, left, and Zimbabwean President Robert Mugabe appear together on Dec. 12, 2014. Mugabe has been president since 1987, but is just three months shy of his 94th birthday, making the question of succession an issue for his Zanu-PF party. (Tsvangirayi Mukwazhi/Associated Press)

At the weekend, both Mugabe and his wife used political rallies to suggest that Mnangagwa would be fired.

Speculation is now swirling over whether Grace Mugabe will be appointed to the vacant vice-president's post at a  congress next month for the Zimbabwe African National Union – Patriotic Front Party (Zanu-PF). On Sunday, she said at a rally that she was ready to take over from her husband.

"So I have said to the president: 'You can also leave me in charge,"' she said. "'Give me the job and I will do it very well because I am good. I can do a great job."'

Now 52, she has been a controversial figure in her own right for extravagant spending in a country with significant poverty and unemployment, and for assault allegations from incidents in London and South Africa. She escaped charges both times due to diplomatic immunity.