At least 30 people have died, while 20 remain missing after flooding and landslides caused by the passage of tropical storm Cheneso battered Madagascar.

Tens of thousands of people were also left homeless across the Indian Ocean island nation, according to a provisional assessment Monday.

The storm made landfall in the northeast of the island last Thursday and impacted close to 89,000 people, Madagascar's National Office for Risk and Disaster Management said.

Madagascar's meteorological agency said the storm, which has now passed across the country into the Mozambique Channel, saw winds gusting up to 170 kph (105.63 mph) and unleashed torrential rains.

Colonel Faly Aritiana, of the risk and disaster office, said there had been house collapses and landslides in which people have become trapped.

"People have been reacting generally in the right way, but some people have not been taking enough note of our warnings not to cross rivers in flood because the flow is much stronger than usual," Aritiana said.

The storm has damaged infrastructure, with many roads cut by rising waters, landslides and collapsed bridges.

Nearly 33,000 people have had to leave their homes in the Boeny region, in the northwest of the island. Locals say the prices of basic foodstuffs have skyrocketed.

"Prices of vegetables and rice increased a lot after the storm" with the cost of tomatoes quadrupling, said Véronique Mamitiana, a teacher in the city of Mahajanga. "The merchants say it’s because the national road is cut," she said.

Marovoay, 100 kilometers (60 miles) further south, was one of the regions worst hit by the storm, with stagnant flood waters still affecting many localities. District leader Tolotriniaina Rakotonindriana said the water level is decreasing very slowly.

"Many houses are still flooded and that is why most of the victims are still in the accommodation sites," Rakotonindriana added. "Roads are covered with water and we have to travel by canoe."

Local authorities said essential food supplies are being distributed to help support those in need.