What you need to know:
- Mr Ncube, who was in charge of the feared Central Intelligence Organisation, was a close ally of the 78-year-old president.
- Mr Ncube becomes the fifth minister to be fired by President Mnangagwa since he came to power five years ago.
Zimbabwe President Emmerson Mnangagwa has fired his State Security Minister "for inappropriate conduct."
President Mnangagwa's office announced the sacking of Owen Ncube on Monday in a brief statement amid speculation that the two fell out over violence that rocked the ruling Zanu PF's recent internal elections.
However, the president's office did not give any reasons for the former minister's sacking.
A week ago, the ruling party held its first internal elections since the 2017 coup that toppled long time ruler Robert Mugabe, who was replaced by President Mnangagwa.
Mr Ncube, who as State Security minister, was in charge of the feared Central Intelligence Organisation, was a close ally of the 78-year-old president.
Mr Ncube was considered to be among the hardliners in President Mnangagwa's government and was accused by the United States as well as the United Kingdom of behind the violent clampdowns against the regime's critics.
In January 2019, he ordered a three-day internet shutdown during protests against steep fuel price increases.
The US responded by adding the minister on its sanctions list for gross violations of human rights.
"In his role as the minister of national security, (Mr) Ncube, with the support of other Zimbabwean government officials, ordered the Zimbabwean security services to identify, abduct and mistreat individuals assessed to be supporters of a Zimbabwean opposition group," the US State Department said at the time.
"In addition, while in his position, the government of Zimbabwe has at times used so-called 'ferret teams' to abduct and beat individuals deemed to be a threat to the ruling Zimbabwe African National Patriotic Front (Zanu PF).
"(Mr) Ncube is being designated for being responsible for or participating in human rights abuses related to political represssion in Zimbabwe."
The UK gave the same reasons when it placed the former minister and other security chiefs under targeted sanctions last year.
Mr Ncube becomes the fifth minister to be fired by President Mnangagwa since he came to power five years ago.