Johannesburg - President Jacob Zuma has denounced any unconstitutional take over of government in Zimbabwe.Zuma who is the chair of the regional body SADC said the body stands ready to assist in the political impasse currently gripping the country."Presidency 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. President Robert Mugabe and his wife Grace are under heavy guard after soldiers cordoned off the parliament building and the defence headquarters as the security situation deteriorates in the southern African country. The military that earlier took over the public broadcaster ZBC is now in charge, with Finance Minster Ignatius Chombo said to have been arrested."The President has urged the government of the republic of Zimbabwe and the Zimbabwe Defence Force to resolve the political impasse amicably and has urged the Zimbabwean Defence Force to ensure that the maintenance of peace and security in the country is not compromised," the presidency said.The statement has not indicated if Zuma has had any communication with his counterpart.Political tensions within Zanu-PF exploded after Mugabe fired his vice President Emmerson Mnangagwa. It followed numerous attack of Mnangagwa by the first lady Grace who is said to be eyeing the presidency ahead of the Zanu-PF congress in December.