"Major Generals Martin Chedondo, Douglas Nyikayaramba, Anselem N Sanyatwe and Air Vice Marshal Shebba Shumbayawonda are set to join the Ministry of Foreign Affairs," presidential chief secretary Misheck Sibanda told the state-run Herald newspaper.

The focus of rumours of a power tussle, Mangagwa's deputy Constantino Chiwenga, has not been seen in public in weeks, prompting speculation about his health.

On Saturday, Mnangagwa told a rally that Chiwenga "is not feeling well.

"So that is why he is not with us here. We thought it would be important to officially make this announcement," the state-run Sunday Mail quoted the president as saying.

Chiwenga was in charge when the police and military cracked down on public protests last month following the government's decision to double fuel prices.

Mnangagwa was in Russia courting investors at the time and was compelled to cancel a planned trip to the World Economic Forum at Davos, Switzerland.

Human Rights Watch (HRW) regional analyst Dewa Mahvinga has said there could be "tensions" between the president and his deputy over control of Zimbabwe's economic levers, including fuel prices.

Mnangagwa did not say what Chiwenga was ailing from, or where he was convalescing.