Zimbabwean President Emmerson Mnangagwa Photo: Ben Curtis/AP

Zimbabwean President Emmerson Mnangagwa says those who illegally shifted money outside the country should repatriate it within three months or face arrest.

Mnangagwa, who took over last week after Robert Mugabe's resignation, describes the move as a "first step towards the recovery of the illegally externalised funds".

He does not say how much money was moved abroad, but the governor of the Reserve Bank of Zimbabwe last year said $1.8 billion had been "externalised" in 2015.

Mnangagwa says his new cabinet will be leaner and more efficient.

According to the state-controlled Zimbabwe Broadcasting Corporation, Mnangagwa met top civil servants Tuesday and told them his new cabinet will be smaller and concentrate on achieving economic growth. 

He did not say when he will announce the new cabinet.

"Our people have endured economic hardships for over two decades, and now expect this new government to turn things around within the shortest time possible. 

"Let us take advantage of the positive optimism among our people, ushered in by this current dispensation, and do our best," said Mnangagwa.

Meanwhile, the wife of a missing Zimbabwean activist, who was abducted by suspected state agents in 2015 after urging then president Mugabe to resign, says she hopes the country's new leader will shed light on what happened to her husband.

Sheffra Dzamara said on Tuesday she still hopes her husband, Itai Dzamara, is alive and that those who kidnapped him will return his body if it turns out that he is dead.

Dzamara's brother, Patson, says Mnangagwa was justice minister at the time of his brother's disappearance and was complicit with human rights abuses and other wrongdoing during Mugabe's rule.

Since becoming president, Mnangagwa has called for national reconciliation, but has not addressed allegations of human rights violations while he was a top official in Mugabe's government.