President Jacob Zuma. Picture: Reuters/Siphiwe Sibeko

Johannesburg - President Jacob Zuma expressed hope on Wednesday that there would not be unconstitutional changes of government in Zimbabwe after the military seized power in Harare.

On Wednesday morning, Zimbabwe's military announced it had seized power in a targeted assault on "criminals" around President Robert Mugabe who were causing social and economic suffering, but gave assurances the 93-year-old leader and his family were "safe and sound".

Zimbabwean soldiers and armoured vehicles blocked roads to the main government offices, parliament and the courts in central Harare, a Reuters witness revealed.

Zuma in a statement called for the Zimbabwean government and army to resolve their differences amicably and said the Southern African Development Community (SADC), on whose behalf Zuma was speaking, was ready to help resolve the impasse in Zimbabwe.

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"President Zuma has called for calm and restraint and has expressed hope that developments in Zimbabwe would not lead to unconstitutional changes of government as that would be contrary to both SADC and African Union positions," the Presidency said.