Floods are ravaging southern Africa, washing away thousands of homes, damaging crops and leaving people stranded on rooftops.

In Mozambique on Friday, authorities put the country on high alert, as flood waters threatened the homes of more than 55,000 people.

The main road between Mozambique and neighbouring Zimbabwe has already been cut off by rising waters and rescue workers have been retrieving people from rooftops and trees.

Mozambique government official Lucas Chomera said 13,000 people have been evacuated from critical areas in Mozambique and moved to government shelters or higher ground.

Chomera said the floods are the result of a rainy season that began earlier than usual in the south and central areas of the country. He said some areas received six months worth of rain in October and November.

Zimbabwe, Zambia hit hard

Severe flooding is also affecting Zimbabwe and Zambia, where at least 21 people have been killed and thousands left homeless in the past month, the British Broadcasting Corporation reported Friday.

Thousands of homes near Harare, in Zimbabwe, have been washed away and the Red Cross is warning that an outbreak of malaria and cholera is possible.

Meanwhile, the floods are taking an economic toll in Zimbabwe, as livestock are being killed by high waters and agricultural specialists say the rain is causing crops to show signs of nitrogen deficiency, the BBC reported.

In southern Zambia, the Magoye River burst its banks, flooding homes and farmland and displacing about 1,000 families. 

With files from the Associated Press