Zimbabwe latest: Emmerson Mnangagwa urges Mugabe to quit now
Zimbabwe's former vice-president, whose sacking led to last week's army takeover, has urged President Robert Mugabe to resign immediately.
Emmerson Mnangagwa said he fled abroad two weeks ago when he learned of a plot to kill him, and he would not return until he was sure of his security.
The ruling Zanu-PF party is expected to begin impeachment proceedings in parliament later on Tuesday.
Mr Mugabe is accused of allowing his wife to "usurp constitutional power".
Speaking from an undisclosed location on Tuesday, Mr Mnangagwa said the 93-year-old president should heed the "clarion call" of his people and step down.
"I told the President that I would not return home now until I am satisfied of my personal security, because of the manner and treatment given to me upon being fired," he said in a statement.
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Mr Mnangagwa's dismissal earlier this month was seen by many as clearing the way for Mr Mugabe's wife Grace wife to succeed him as leader.
The move riled top army officials, who stepped in and put Mr Mugabe under house arrest, though he nominally remains the president.
Vicious power struggle
Andrew Harding, BBC News, Harare
Emmerson Mnangagwa more or less accused President Mugabe of trying to have him killed. The statement from the former vice-president gave an extraordinary insight into the vicious power struggles that preceded last week's military intervention here.
Mr Mnangagwa said his security guards had warned him of plans to "eliminate" him, after he was sacked earlier this month. He promptly fled to South Africa.
On Monday night Zimbabwe's army generals claimed that Mr Mnangagwa had agreed to return home as part of a transitional roadmap.
That roadmap now sounds like wishful thinking, as parliament here prepares to impeach the president, and Mr Mnangagwa angrily demands that his former boss respects the will of the people or faces humiliation.
What is President Mugabe accused of?
Impeachment in Zimbabwe can only occur in specific scenarios, on grounds of "serious misconduct", "violation" of the constitution or "failure to obey, uphold or defend" it, or "incapacity".
On Monday, Zanu-PF member of parliament Paul Mangwana said: "The main charge is that he has allowed his wife to usurp constitutional power when she has no right to run government."
"He has refused to implement the constitution of Zimbabwe – particularly we had elections for the provincial councils, but up to now they have not been put into office."
How would the impeachment process unfold?
It would start with a motion, to be presented as early as Tuesday afternoon, laying out the charges against Mr Mugabe and his wife.
If – as is likely – the motion is approved by a 50% majority in a joint sitting of the National Assembly and the Senate, a committee from both chambers will be appointed to investigate.
Should the committee support the charges, the president can then be removed if both houses back them with two-thirds majorities.
Paul Mangwana said the process could be fast-tracked and completed by Wednesday, "because the charges are so clear". But others insist the process should take longer.
Tendai Biti, a leading member of the opposition MDC, told the BBC that the constitution allows for a fair hearing, and "Mugabe as the accused person will obviously be entitled to legal representation".
The full process, Mr Biti added, could take between one and three weeks. If the impeachment is fast-tracked, he said, "the process will not be legitimate or credible".
What happens if Mr Mugabe is removed?
He will be replaced by the vice-president . The military, which supports Mr Mnangagwa, would like to see him step into that role.
But when he was removed from office, Phelekezela Mphoko – a known supporter of Grace Mugabe – became vice-president, and in theory would assume the presidential role.
It is not clear if Mr Mnangagwa could be restored to his former position, and military leaders simply said the public would "be advised on the outcome of talks" between Mr Mugabe and his former deputy.