Zimbabwe's military has stormed the country's national broadcaster's studios to declare it is 'targeting criminals' amid fears of a coup after reports of explosions and gunfire in the capital.

The military read a statement on live TV claiming this not 'a military takeover of government' and President Robert Mugabe was safe.

The US Embassy in Zimbabwe had ordered employees and US citizens in the African nation to take cover and seek shelter on Tuesday after gunfire was heard near the home of the 93-year-old president, sparking fears of an armed military take over.

Soldiers stormed the headquarters of state broadcaster ZBC in the early hours of Wednesday, two members of staff and a human rights worker told Reuters, as staff complained they were manhandled by the military members.

After taking control of the station, the military released a statement which denied a coup was underway adding that Mugabe and his family were 'safe and sound and their security is guaranteed'.

They said that the army were targeting people who 'were committing crimes that are causing social and economic suffering in the country.

'As soon as we have accomplished our mission, we expect that the situation will return to normalcy,' the statement continued.

Zimbabwe's envoy to South Africa, Isaac Moyo, had earlier reported there was no coup, adding that the government was 'intact'.

Fears of a coup had sent shockwaves around Zimbabwe after at least three explosions were heard in Harare.

Armed soldiers were also reportedly seen assaulting passers-by in the capital and loading ammunition near a group of four military vehicles in an unprecedented challenge to Mugabe.

The Zimbabwean President's house, where gunfire was heard this morning, was also surrounded by soldiers, but speculation suggested it was for his own protection amid suggestions his 37-year reign was coming to an end.

Tanks had been making their way to the city centre throughout the day yesterday as tensions reached boiling point.

Zimbabwe's head of the military said he could 'step in' to end President Mugabe's 'purge' of opponents on Monday.

This prompted the ruling ZANU-PF party to say it would never succumb to military pressure and described the statement by the armed forces chief as 'treasonable conduct'.

Mugabe plunged the country into crisis last week by sacking vice-president Emmerson Mnangagwa, widely seen as a power move to make way for his wife Grace to succeed him.

In Harare in the early hours of this morning, aggressive soldiers told passing cars to keep moving through the darkness.

'Don't try anything funny. Just go,' one barked at a reporter on Harare Drive.

Two hours later, soldiers overran the headquarters of the ZBC, Zimbabwe's state broadcaster and a principal Mugabe mouthpiece, and ordered staff to leave.

Several ZBC workers were manhandled, two members of staff and a human rights activist said.

Shortly afterwards, three explosions rocked the centre of the southern African nation's capital, witnesses said.

Despite the troops stationed at locations across Harare, there was no word from the military as to the fate of Mugabe, Zimbabwe's leader of the last 37 years and the self-styled 'Grand Old Man' of African politics.

The US embassy in Zimbabwe on Wednesday warned its citizens in the country to 'shelter in place' due to 'ongoing political uncertainty' as the crisis deepened.

'US citizens in Zimbabwe are encouraged to shelter in place until further notice,' the embassy in Harare said in a statement.

Tanks rolled into Zimbabwe's capital last night, leaving the nation in political chaos as its army chief was accused of attempting a coup.

The turmoil in Harare was an unprecedented test of dictator Robert Mugabe's 37-year grip on power.

It came a day after the country's most powerful generals warned the 93-year-old president he risked a coup if he continued a purge of senior figures in his ruling Zanu-PF party.

Many fear the sackings could clear the way for his wife Grace, 52, to succeed him.(DailyMail)