The army say Zimbabwe’s president Robert Mugabe is "safe" after gunfire was heard near his compound and troops seized control of the state broadcaster.
Loud explosions were heard in Harare in the early hours of Wednesday after military vehicles rolled into the capital, prompting speculation of a coup.
The blasts and gunfire came hours after a military chief warned the army could step in amid a political crisis sparked by 93-year-old Mr Mugabe firing his vice president – and likely successor – Emmerson Mnangagwa earlier this month.
General Constantino Chiwenga, commmander of Zimbabwe’s defence forces, had demanded an end to a purge in the ruling ZANU-PF party – which appeared to be paving the way for Mr Mugabe’s 52-year-old wife Grace to succeed him.
In a statement read on state TV, a member of the armed forces told the Zimbabwean people: Comrade Mugabe and his family are safe and sound and their security is guaranteed.
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.
General Chiwenga – who Mr Mugabe had accused of treason for his intervention – spoke on national radio.
He said: To both our people and the world beyond our borders, we wish to make it abundantly clear that this is not a military takeover of government.
What the defence forces are doing is to pacify a degenerating political social and economic situation in our country, which if not addressed may result in a violent conflict.
He said all military leave had been cancelled – ordering members of the armed forces to return to their barracks.
He appealed to war veterans and tribal leaders for support and issued a veiled threat to the country’s security services, telling them: We urge you to cooperate for the good of our country – let it be clear that we intend to address the human security threats in our country therefore any provocation will be met with an appropriate response.
A Foreign Office spokesperson said: We are aware of reports of military vehicles moving on the outskirts of Harare. We are monitoring the situation closely and keeping travel advice under regular review.
We advise any British national in Zimbabwe who may be concerned to monitor our travel advice for changes.
The US State Department urged its citizens to shelter in place during the crisis.
Mr Mnangagwa, 75, a veteran of the liberation wars, fled to South Africa after he was ousted on 6 November – with President Mugabe accusing him of plotting against the government.
Mr Mugabe is the only leader Zimbabwe has known in 37 years of independence.
On Tuesday, Reuters, AFP and AP witnesses said they saw several military vehicles, thought to be armoured personnel carriers, heading along roads towards the capital.
Reuters said another two military vehicles had been seen parked beside the road from Harare to Chinhoyi, about 20 miles from the capital and Sky News has obtained pictures said to show caterpillar-track armed vehicles between Norton and Harare.
It was not immediately clear why the vehicles were on the move, with analysts saying the vehicles may have been on routine manoeuvres.
Soldiers were seen at the scene, but they refused to talk to journalists.
On Monday, General Chiwenga said: We must remind those behind the current treacherous shenanigans that, when it comes to matters of protecting our revolution, the military will not hesitate to step in.
The current purging … targeting members of the party with a liberation background must stop forthwith, he said.
Mrs Mugabe, 52, has a strong following in the powerful youth wing of ZANU-PF.
Her rise has been seen as a challenge to the dominance of the independence-era war veterans, who previously held privileged positions in the ruling party under Mr Mugabe.
The veterans, some of who took part in the civil war in the former British colony, have increasingly been prevented from holding senior government and party roles in recent years.