Huge challenges include “disruptions to food-supply chains, to the fuel transport, to the medical access, because most of the major roads are cut”, he added.
One resident described to the BBC how she and her family cowered inside as wind and rain lashed their home for six hours straight, before the windows smashed and water poured in.
“We are trying to do our best… It’s dangerous and I don’t know if there will be enough people to help us, even though the authorities are trying,” the woman, who gave her name as Denise, told BBC Newsday.
“It’s real and its worse” than it looks in videos being shared online, she added.
Gezani is the second cyclone to hit Madagascar this year. It comes 10 days after tropical cyclone Fytia killed 14 and displaced over 31,000 people, according to the UN’s humanitarian office.
The island’s rulers are now pleading for international help.
“What happened is a disaster, nearly 75% of the city of Toamasina was destroyed,” the country’s military leader Colonel Michael Randrianirina, who seized power in October, told the AFP news agency.
“The current situation exceeds Madagascar’s capabilities alone,” he added.
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, AFP reports.
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).
“It’s total chaos, 90% of house roofs have been blown off, entirely or in part,” the head of disaster management at the Action Against Hunger aid agency, Rija Randrianarisoa, told AFP.
All acknowledge that a huge amount of work needs to be done.
“It takes many, many years” to restore infrastructure and recover, Environment Minister Andonirina told the BBC, adding that parts of Madagascar ravaged by cyclones in the past three years still “have not been rebuilt as it was before”.