"It's monstrous. Everything is devastated, roofs have been blown off, floors are flooded, the walls of solid houses have collapsed," a resident of Toamasina, on Madagascar's east coast, told AFP by telephone during a brief return of connection.

"And I'm talking about the nice neighbourhoods, with well-built houses," said the source, who had been left without electricity since the afternoon, five hours before the cyclone hit.

In its latest update, the CMRS cyclone forecaster on France's Reunion island confirmed that Toamasina had been "directly hit by the most intense part" of the storm.

Schools in several of the island's regions will be shut on Wednesday, which the government has declared a non-working day as a precaution.

Although Gezani lost steam and was downgraded to the level of a tropical storm as it headed into inland Madagascar, it is expected to pick up back to cyclone speeds on its way across the channel to Mozambique.

Colonel Michael Randrianirina, in power in Madagascar since an October military coup, said he would make his way to Toamasina to be closer to the people at the time of Gezani's passing.

According to the CMRS, the cyclone's landfall was likely one of the most intense recorded in the region during the satellite era, rivalling Geralda in February 1994.

That storm left at least 200 dead and affected half a million more.