Zimbabwean President Emmerson Mnangagwa has reportedly said that his call last year for the return of externalised funds is "being heeded and substantial millions" have been returned.

A report by the state-owned Herald newspaper on Tuesday quoted Mnangagwa, who spoke on the sidelines of his state visit to Namibia this week, as saying that millions of looted funds were being returned.

It was, however, not immediately clear how much had been returned so far.

Mnangagwa maintained that the southern African country was addressing its challenges with "renewed effort and vigour".

Mnangagwa announced in November a 90 day amnesty for the return of funds siphoned out of the country by individuals and corporations during ex-president Robert Mugabe's reign.

The president said at the time that those who returned their illegally earned cash were going to be pardoned unconditionally. The amnesty period was set to run from December 1 until March.

"Upon expiry of the three-month window, the government will proceed to effect arrest of all those who would not have complied with this directive and will ensure that they are prosecuted in terms of the country's laws," Mnangagwa was quoted as saying at the time.

Mnangagwa, who took over from long ruling Mugabe after a military intervention, said the operation had discovered that huge funds were illegally externalised.

Mnangagwa was sworn-in in November last year and has vowed to fight corruption, protect foreign investment and create jobs to help re-build the troubled economy.