President Robert Mugabe and his family have been detained following military intervention in capital Harare, which an army spokesman and the ruling party insisted Wednesday was "not a coup".
Zimbabwe's envoy to South Africa, Isaac Moyo, earlier dismissed talk of a coup, saying the government was "intact".
Referring to Mugabe, who has held power since 1980, he said: "We are only targeting criminals around him who are committing crimes that are causing social and economic suffering in the country in order to bring them to justice".
In the army's overnight broadcast, the spokesman, Gen. Sibusiso Moyo, said the military expected "normalcy" to return as soon as the army had completed its "mission".
On Tuesday afternoon (local time), witnesses said they saw a number of tanks turn before reaching Harare, heading towards the Presidential Guard compound in a suburb called Dzivarasekwa on the outskirts of Harare.
"As a country that is friendly with Zimbabwe, we are paying close attention to developments of the situation in Zimbabwe", Geng added.
The statement from the ZANU-PF party was released amid worries that the military might be taking action to oust Mugabe.
Mnangagwa had previously been seen as Mugabe's successor but was replaced by the president's wife, Grace Mugabe, as the favorite, resulting in a split in the Zanu-PF.
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The US embassy has warned its nationals to "shelter" amid uncertainty and wait for further notice, according to its website.
The southern African nation had been on edge since Monday when Chiwenga, Commander of the Zimbabwe Defence Forces, said he was prepared to "step in" to end a purge of supporters of sacked vice president Emmerson Mnangagwa.
Mnangagwa, who had fled into exile, has vowed to return and launched a direct challenge to Mugabe by calling for members of the ruling Zanu-PF party to desert the President.
The leader of Zanu-PF's youth wing, Kudzai Chipanga, told reporters: "It is our country and future at stake and we will not let any individual military man interfere with the leader of the party and legitimately voted president of this country".
Tensions between the veteran leader and the military, which has long helped prop up his authoritarian rule, have erupted in public in recent days.
Zimbabwe's President Robert Gabriel Mugabe addresses the U.N. General Assembly at the United Nations on September 21, 2017, in New York, New York.
Grace Mugabe has drawn the ire of Zimbabweans for appearing to be out of touch.
The Army last night announced that they had taken over government business, with the intension of dealing with President Mugabe's ministers who were misleading the aged leader.