Soldiers have taken over the headquarters of Zimbabwe's national broadcaster, ZBC, amid a growing political crisis.

Explosions were heard in the capital, Harare, earlier after military vehicles rolled into the city.

The army say the President Robert Mugabe is "safe".

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 said all military leave had been cancelled - ordering members of the armed forces to return to their barracks.