One of Zimbabwe's senior Catholic clerics has said his country faces a "leadership vacuum" as President Robert Mugabe becomes increasingly incapable because of age and ill health.

Fr Frederick Chiromba, secretary-general of the Catholic Bishops' Conference of Zimbabwe, said the country was being damaged because of the uncertainty about who would replace 92-year-old Mugabe and how the transition would be managed.

He said in a Vatican Radio interview explaining the context of the recently-published ecumenical Church leaders' statement on the national crisis in Zimbabwe: "Biologically things come to a stage in life where somebody can no longer fully function in certain offices and hence even the Churches were calling for that review, that leadership renewal."

He said weak leadership was leading to a "jostling for power". "Really this puts the nation in a very precarious situation because you don't know... if there is no clear structure, which way things will go."

He appeared dismissive of the #ThisFlag protest movement started by Pastor Evan Mawarire, saying "people are hoping for some salvation, for a way out of this situation".

"I wouldn't give much credit to the This Flag movement except that it has captured the imagination of the people about what is possible," he said.

He also appealed for the lifting of international sanctions against Zimbabwe, saying they did no harm to the people responsible for the country's plight.

"Their children are overseas studying in those countries which imposed the sanctions in the first place. And when they fall sick they are not treated in the country, they go outside the country where they get good health facilities," he said.

Zimbabwe's economy and institutions have been destroyed under the catastrophic Mugabe regime. Unemployment has risen to 95 per cent and 80 per cent of the population live in poverty.