Cyclone Batsirai killed at least 10 people and displaced nearly 48,000 when it struck Madagascar overnight, the national disaster management agency said on Sunday.

The cyclone later weakened but not before wreaking havoc in the poor Indian Ocean island nation which is still reeling from a deadly tropical storm earlier this year.

Parts of the country were lashed with heavy rains and wind before the cyclone made landfall in Mananjary.

It uprooted trees, destroyed buildings and forced residents to weigh down flimsy corrugated iron roofs along its path, AFP correspondents saw.

The rain will cause flooding across parts of the country, Madagascar's meteorological office said on Sunday.

Batsirai made landfall late Saturday as an "intense tropical cyclone", packing winds of 165 kilometres (102 miles) per hour, Faly Aritiana Fabien of the country's disaster management agency told AFP.

His colleague responsible for risk management, Paolo Emilio Raholinarivo, listed 10 dead but gave no further details.

However, the national meteorological office -- which had warned of "significant and widespread damage" -- said on Sunday that Batsirai had weakened.

At a cemetery in the eastern town of Mahanoro, overlooking the sea, Marie Viviane Rasoanandrasana sat on the ground watching over the bodies of her husband, father-in-law and daughter.

The waves of the rising sea eroded the sandy hill which was part of a graveyard. Several graves were ripped open, exposing their bodies and some others.

"A few days ago the sea was far away, but this morning I was told the waves had washed away part of the cemetery," said the 54-year-old widow.

"Daily life is already very hard," she said, adding the family would be forced to rebury the remains in a temporary grave until they raise enough money for a "proper burial".

"Mananjary is completely destroyed, no matter where you go everything is destroyed," said one resident named Faby. Another man, Fana, was certain "almost 95 percent of the city has been destroyed"

Inland in Antsirabe, 365 km northwest of Mananjary, the storm uprooted large trees in the town's public park.

The Meteo-France weather service had earlier predicted Batsirai would pose a "very serious threat" to Madagascar, after passing Mauritius and drenching the French island of La Reunion with torrential rain.

Some 10,000 people on La Reunion were still without electricity on Sunday, three days after the tropical cyclone passed through the island, injuring 12 people on its path.

Ana affected at least 131,000 people across Madagascar in late January, with nearly 60 people killed, mostly in the capital Antananarivo.

Ana also hit Malawi, Mozambique and Zimbabwe, causing dozens of deaths. The World Food Programme, citing estimates from national authorities, said around 595,000 people could be directly affected by Batsirai, and 150,000 more might be displaced because of new landslides and flooding.

The storm poses a risk to at least 4.4 million people in total, the International Federation of Red Cross and Red Crescent Societies said.

The former French colony off Africa's southeastern coast is in the midst of a six-month rainy season that often results in casualties and widespread damage.

In 2018, the country suffered a double whammy with Cyclone Ava killing 51 people in January and tropical storm Eliakim leaving 20 people dead two months later.

And in March 2017, at least 78 people perished in Cyclone Enawo. Global warming has increased the risk of flooding and tropical storms, as the atmosphere retains more water and rainfall patterns are disrupted.

Southern parts of Madagascar are reeling from the worst drought in four decades. South Africa's President Cyril Ramaphosa told a summit of African leaders meeting in Addis Ababa on Sunday that the continent was "experiencing the worst impacts of phenomena associated with global warmings such as droughts, floods and cyclones". "Despite not being responsible for causing climate change, it is Africans who are bearing both the brunt and the cost," he said.