Mozambique braced for flooding, high winds, sea surges and evacuations on Wednesday as Cyclone Dineo neared the coast, with forecasters predicting widespread damage.

Dineo was set to make landfall in the southern province of Inhambane in the evening, packing winds of about 130 kilometres (80 miles) an hour, the South African Weather Service (SAWS) said.

Mozambique's meterological services upgraded the storm to a tropical cyclone on Wednesday afternoon as strong winds began to slam into coastal areas.

Torrential rain, flooding and a coastal storm surge were expected, with SAWS warning that Dineo was "a formidable storm system which has the potential to cause much damage to coastal and inland infrastructure".

The Mozambique Red Cross dispatched emergency relief supplies and 350 workers to areas likely to be in the impact zone, where rivers are already at flood level.

"Many of the districts likely to be hit have been inundated by above-normal rainfall since early January," Jamie Le Sueur, Red Cross disaster management coordinator for southern Africa, said.

The Red Cross warned that flooding could also contaminate water sources and spread sickness after the storm passes.

- Seeking shelter -

Mozambique's National Institute of Disaster Management (INGC) issued an alert over the cyclone threat, advising people to prepare food and water supplies and urging vulnerable communities to seek shelter.

The INGC said it was also planning evacuation routes.

Local media reported that flooding was expected in the southern cities of Inhambane and Maxixe as well as in many villages, with houses, crops, roads and livestock at risk as well as human lives.

Officials advised people to turn off electricity and stay away from power cables to avoid shocks, and to protect windows with wood or plastic.

Heavy rains will spread into South Africa, Zimbabwe and Botswana on Thursday and Friday as the cyclone weakens, forecasters say.

Mozambique, one of the world's poorest countries, is often battered by deadly flooding and storms.

In 2000, floods claimed at least 800 lives, and more than 100 were killed in 2015.

Scores have already died in the current rainy season, which began in October.

The high death toll in 2000 triggered donor funding for relocations and improvements to water management infrastructure, early warning systems and emergency response resources.