Troops in Zimbabwe's capital Harare have reportedly seized the country's state broadcaster ZBC and loud explosions have been heard in the city, prompting further speculation of a coup.
Zimbabwe's envoy to South Africa, Isaac Moyo, earlier dismissed talk of a coup, saying the government was "intact".
This came after reports emerging that the Zimbabwean soldiers with Zimbabwe Defense Forces (ZDF) reportedly seized control of the state broadcasting outlet in the wee hours of the Wednesday morning. He said: "We wish to assure the nation that his Excellency, the president... and his family are safe and sound and their security is guaranteed".
"We are only targeting criminals around him (Mugabe) who are committing crimes that are causing social and economic suffering in the country in order to bring them to justice", Zimbabwe Major General SB Moyo, Chief of Staff Logistics said.
The US State Department said it was "closely monitoring" the situation in Zimbabwe and urged all parties to resolve disputes "calmly and peacefully".
The ZANU PF Twitter account retweeted a message from the party's youth league that said: "The army is simply effecting a National Democratic Project and it's doing so with peaceful aplomb".
Grace Mugabe - 41 years younger than her husband - has become increasingly active in public life in what many say was a process to help her eventually take the top job.
Zanu-PF, Mugabe's party, gave a statement denying there had been a coup.
For the first time, this southern African nation is seeing an open rift between the military and Mugabe, the world's oldest head of state who has ruled since independence from white minority rule in 1980.
Robert Mugabe has accumulated a net worth of $10 million (£7.5 million) thanks largely to the fortunes reaped from Zimbabwe's diamond deposits.
Zimbabwe's Commander of Defense Forces General Constantino Chiwenga said on Monday he was prepared to "step in" to end a purge of supporters of the sacked vice president.
Political tensions had risen in the country since November 6, when Mugabe fired Emmerson Mnangagwa as vice president, accusing him of showing "traits of disloyalty" and plotting to take power.
Grace Mugabe has drawn the ire of Zimbabweans for appearing to be out of touch.
President Robert Mugabe listens to his wife Grace Mugabe at a rally of his ruling ZANU-PF party in Harare.
The US embassy in Harare tweeted that it would be closed on Wednesday "due to ongoing uncertainty".
Grace Mugabe had long-developed a strong following in the powerful youth wing of the ruling party.
President Mugabe, 93, nor his representatives have commented on the latest developments. "It's a question of the military taking over by using the force they have".
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