Two dozen Madagascans have died and tens of thousands been left homeless since a severe tropical storm made landfall last week and swirled for days off the island's western coast, official records showed Sunday.

Cyclone Cheneso smashed into northeastern Madagascar 10 days ago, bringing heavy winds and triggering downpours that have caused extensive flooding.

Over the week it has tracked south-eastwards, extending damage to houses, schools and cutting off several national roads.

Twenty-five people are now known to have died and 21 others are still missing, according to an update from Madagascar's risk management office.

At least 83,181 people have been affected, with nearly 38,000 displaced from their homes.

Cheneso -- which temporarily intensified to a tropical cyclone in recent days with winds of 118-166 kilometres per hour (73-103 miles per hour) -- "has started to lose its purely tropical characteristic," according to the southwest Indian ocean Regional Specialist Meteorological Centre based in the French overseas island of La Reunion

Storm Cheneso made landfall on January 19, packing winds of up to 110 kilometres per hour.

It is the first tropical storm of the current cyclone season in southern Africa -- which typically runs from November to April -- to hit the cyclone-prone large Indian ocean island.