At least 20 people have died after a powerful cyclone struck Madagascar, reports the disaster authority in the Indian Ocean island.

Cyclone Gezani made landfall on Tuesday, hitting the island's main port, Toamasina.

Madagascar's disaster management office reported total chaos in the areas worst hit by the storm, where many houses collapsed. Much of the city was plunged into darkness after power lines were damaged, while trees were uprooted and roofs ripped off.

According to the CMRS cyclone forecaster on France's Reunion island, the cyclone could be one of the most intense to impact the city in the satellite era.

The National Office for Risk and Disaster Management indicated many fatalities occurred when houses fell due to the storm. Cyclone Gezani, with winds reaching 250 km/h (155 mph), battered Toamasina, which is Madagascar's second-largest city.

It's total chaos; 90% of the roofs have been either entirely or partially blown off, said the head of disaster management with Action Against Hunger, Rija Randrianarisoa.

Emergency responders have started evacuating injured persons and hundreds of residents from the district surrounding Toamasina, home to around 400,000 people.

Residents described experiencing unprecedented violent winds, significantly worse than in previous storms.

Gezani is the second cyclone to hit Madagascar this year, following tropical cyclone Fytia, which resulted in 14 deaths and displaced over 31,000 individuals.

In anticipation of the cyclone's arrival, officials in Madagascar shut down schools and set up emergency shelters throughout the affected regions.

As of Wednesday morning, Madagascar's meteorological service reported that Gezani had weakened to a moderate tropical storm and was moving inland, approximately 100 km north of the capital, Antananarivo, before heading towards the Mozambique Channel.

The nation's leader, Colonel Michael Randrianirina, who came to power in October, visited Toamasina to assess the storm's impact.

Cyclone season in this region typically spans from November to April, often bringing a series of storms each year.