The death toll from Cyclone Chido's rampage through the French overseas territory of Mayotte remained unclear on Wednesday, with shantytowns that were home to undocumented migrants flattened and many areas still inaccessible.

Local officials and health workers have said hundreds or even thousands could be dead from the worst storm to hit the Indian Ocean archipelago in 90 years. But only 22 fatalities recorded in hospital have been confirmed so far.

"I cannot give a death toll because I don't know. I fear the toll will be too heavy," acting Interior Minister Bruno Retailleau told BFMTV on Wednesday.

Some victims were buried before their deaths were counted and authorties are still unable to reach some areas.

The situation is made more difficult by uncertainty around the exact size of Mayotte's population. While official statistics put it at 321,000, many believe it is much higher due to undocumented immigration, mainly from Comoros and Madagascar.

Authorities were ramping up relief operations, with 120 tonnes of food due to be distributed on Wednesday. Supplies have bene arriving via an air bridge from France's other Indian Ocean territory, Reunion Island.

Retailleau also said two gendarmes were injured overnight by projectiles during a curfew decreed on Tuesday in response to reported looting and lawlessness. Mayotte is France's poorest overseas territory and has experienced repeated bouts of unrest in recent years.

In the morning, residents of the capital Mamoudzou whose houses survived the storm hammered metal sheets to cover damaged roofs. Thousands of flimsier huts across the city's shantytowns were razed entirely, leaving fields of dirt and debris.

The ferry linking Mayotte's two main islands resumed services on Wednesday for civilians, allowing some people caught out by the storm to return to their families.

"I haven't heard a word from my employees in five days," said a land owner taking the ferry, who declined to give his name. "It's back to the Stone Age."

RELIEF OPERATIONS

Health workers say they are bracing for a surge of disease as dead bodies lie unrecovered and people struggle to access clean drinking water. The French government said on Tuesday evening there were no outbreaks at this point.

Chido also killed at least 34 people in Mozambique and 13 in Malawi after reaching continental Africa.

Pope Francis mentioned the storm during his weekly audience at the Vatican, asking that God "grant rest to those who lost their lives, necessary assistance to those who are in need, and comfort to the families who have been affected".

French President Emmanuel Macron will visit Mayotte on Thursday. Opposition politicians in France have criticised what they say is the government's neglect of Mayotte and failure to prepare for natural disasters linked to climate change.

Some hard-right politicians, including Retailleau of the conservative Republicans party, have pointed the finger at illegal immigration, which they say has impoverished Mayotte and left it with vast shantytowns vulnerable to extreme weather.

Concerns about immigration and inflation have helped make the territory a stronghold for the far-right National Rally with 60% voting for Marine Le Pen in the 2022 presidential election runoff.