Zimbabwean generals say they have seized control to take power away from "criminals" around President Robert Mugabe.
The crisis came a week after Mr Mugabe sacked his deputy, Emmerson Mnangagwa, in favour of his wife, Grace.
Army chief Gen Constantino Chiwenga warned on Monday that the military would step in and take action if such "purges" in the ruling Zanu-PF party did not stop.
Who are the key players in this crisis?
A revolutionary hero who spent years in jail for the "liberation" struggle, he came to power in elections after independence was declared in 1980.
This is why, even today, many African leaders remain reluctant to criticise him - unlike a large number of his compatriots who experience his rule first-hand.
Most of the world has moved on from the anti-colonial struggles but Mr Mugabe's outlook and tactics for retaining political control remain the same. He is best-known for his land reform programme in the 1990s that involved the seizure of white-owned farms for redistribution to black peasants.
After decades of authoritarian rule, his country is in political and economic turmoil, and allegations of government corruption are rife. He is viewed globally with derision.
The proud 93-year-old is reluctant to relinquish power but as his physical powers have visibly deteriorated, the battle over his succession has come to the fore.
The independence-era old guard represented by sacked Vice-President Mnangagwa is rivalling the younger "Generation-40" faction fronted by Mrs Mugabe.
Robert Mugabe's second wife, who is more than 40 years his junior, has risen from presidential typist to the most powerful woman in Zimbabwe.
They met and had their first two of three children while Mr Mugabe's first wife, Sally, was terminally ill with cancer, though they only married after her death.
Her alleged appetite for extravagant shopping earned her the moniker Gucci Grace.
While her supporters point to her charitable and philanthropic work and refer to her as "Dr Amai", meaning "mother", her critics accuse her of pursuing a ruthless campaign for wealth and power.
As a notable political figure close to the president, Grace has been subject to the same targeted EU and US sanctions as her husband, which include a travel ban and asset freeze.
She accompanies the president on trips abroad, often visiting the Far East where they own property. Her many domestic business interests also include a dairy farm estate outside Harare, which she claimed as part of the national land reforms implemented starting in 2001.
Mrs Mugabe has a sharp tongue and last week she described her rival, Vice President Mnangagwa, as a "snake" which "must be hit on the head". The next day President Mugabe sacked him.
Until Mrs Mugabe's rise, he had been viewed for several years as President Mugabe's anointed successor.
Following military training in Egypt and China, he helped direct the "liberation" struggles prior to independence in 1980, spending time in jail where he was allegedly tortured. He has been in government ever since.
Thousands of civilians died in a brutal post-independence conflict in which he played a key role as National Security minister, though he denies having blood on his hands.
He is known in Zimbabwe as ngwena (English: crocodile) (and his supporters as "Lacoste") because of his political cunning, biding his time in the 1990s to reclaim a position of power after falling foul of Mr Mugabe and being cast into political oblivion. But his fearsome reputation means he is little loved in the rank-and-file of the Zanu-PF party.
As a former defence and national security minister, he was a key link between the ruling party and Zimbabwe's military and intelligence agencies. He is also chair of the Joint Operations Command, in charge of state security.
Gen Constantino Chiwenga
At 61, he is a close ally of Mr Mnangagwa and has led the army since 1994.
Gen Chiwenga was also a product of the country's independence struggles, training with the Zimbabwe African National Liberation Army in Mozambique and later rising through its ranks.
In 2002, he and 18 other close associates of President Mugabe were sanctioned by the European Union, United States and New Zealand, including a travel ban and freeze on his foreign assets, which has been repeatedly extended. In 2003, he was promoted to commander general of the Zimbabwe combined armed forces.
He shocked Zimbabweans on Monday when he issued an open warning against those responsible for "purging" the ruling party of those who shared his roots in the country's struggles against colonialism, saying the military could step in.
A former mine worker and union chief, the 65-year-old became the symbol of resistance to Mr Mugabe's government during the mid-2000s.
The charismatic public speaker founded the Movement for Democratic Change in 2000 and stood for president in 2008, gaining the most votes but, according to official results, not enough to win outright. He withdrew from the second round after a campaign of violence by Mr Mugabe's security forces.
He was later sworn in as prime minister and in 2013 challenged Mr Mugabe for the presidency again but lost heavily.
Mr Tsvangirai has been brutally assaulted, charged with treason and labelled a traitor and has reportedly survived three assassination attempts, including one in 1997 in which he was nearly forced out of the window of his 10th-storey office.
He has been receiving treatment for cancer in South Africa but returned to Zimbabwe after the army took control and has called for Mr Mugabe to resign.