Cyclone Idai has triggered a "massive disaster" in southern Africa affecting hundreds of thousands if not millions of people, the UN says.

The region has been hit by widespread flooding and devastation affecting Mozambique, Zimbabwe and Malawi.

Mozambique's President Filipe Nyusi has called it "a humanitarian disaster of great proportion".

He said more than 1,000 people may have been killed after the cyclone hit the country last week.