At least 20 people have died after a powerful cyclone struck Madagascar, says 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 said there was "total chaos" - reporting that houses collapsed in the impact zone, where the bodies were found. Neighbourhoods were plunged into darkness as power lines snapped, while trees were uprooted and roofs ripped off.

The cyclone's landfall is likely to have been one of the most intense recorded around the city in the satellite era, according to the CMRS cyclone forecaster on France's Reunion island, cited by AFP.

The National Office for Risk and Disaster Management said many were killed when houses collapsed. Cyclone Gezani hit Toamasina - the country's second-largest city - with winds reaching 250 km/hour (155 mph).