Aid workers scrambled to save hundreds trapped by floods around the Mozambican port city of Beira yesterday, after a powerful cyclone killed hundreds of people and left a trail of destruction across swathes of southeast Africa.

Cyclone Idai hit Mozambique's port city of Beira with winds of up to 170 kph last Thursday, then moved inland to Zimbabwe and Malawi, flattening buildings and putting the lives of millions at risk.

At least 200 people have died in Mozambique and 98 in Zimbabwe, but the death toll is likely to rise as rescuers are still finding bodies.

Hundreds were clinging onto trees or roofs, waiting for rescue teams. Roads in and around Beira were swamped and heavy rain was continuing to fall, complicating rescue efforts and meaning that aid had to be flown in by helicopter or plane.

Mozambican President Filipe Nyusi has declared three days of national mourning starting from yesterday and has said the eventual death toll from the cyclone and ensuing floods could rise to more than 1,000.

In the eastern Zimbabwe, grieving families rushed to bury their dead because the cyclone had knocked out power supplies and put mortuaries out of action.

Zimbabwean President Emmerson Mnangagwa said on a visit to the town of Chimanimani that his government would ensure houses were built with stronger materials in future. In rural Zimbabwe, many people cannot afford cement to build their houses, leaving them vulnerable to torrential rain and wind.

Malawi has not released details of casualties from the storm, which weakened as it moved further inland. More than 50 people had already died in floods the week before the cyclone hit.