Hundreds of people are feared dead in Mayotte after the French Indian Ocean territory was devastated by a powerful cyclone.
Entire settlements were flattened when Cyclone Chido brought wind speeds of more than 225km/h (140mph), with the poorest living in makeshift shelters particularly hard hit.
Rescue workers, including reinforcements from France, are combing through the debris searching for survivors.
Widespread damage to infrastructure - with downed power lines and impassable roads - is severely hindering emergency operations.
Some of Mayotte's population of 320,000 have said they are struggling with severe shortages of food, water and shelter.
One resident of the capital city, Mamoudzou, waiting in a queue for supplies said: "We've had no water for three days now, so it's starting to be a lot.
"We're trying to get the bare minimum to live on, because we don't know when the water will come back."
Another Mamoudzou resident, John Balloz, said he was surprised he did not die when the cyclone struck.
"It was the wind, the wind blowing, and I was panicked, I screamed, 'We need help, we need help.' I was screaming because I could see the end coming for me," he said.
Mohamed Ishmael, who also lives in the capital, told Reuters news agency the situation there was "a tragedy" and said: "You feel like you are in the aftermath of a nuclear war… I saw an entire neighbourhood disappear."
Another said they had used a nearby school for shelter, adding: "We can still take refuge with our neighbours, and we're still sticking together and being cautious. We need everyone to hold hands."
Mayotte's impoverished communities, including undocumented migrants who have travelled to the French territory in an effort to claim asylum, are thought to have been particularly hard hit due to the vulnerable nature of their housing.
Its population is heavily dependent on French financial aid and has long struggled with poverty, unemployment and political instability.
About 75% of the population live below the national poverty line and unemployment hovers at around one in three.
French President Emmanuel Macron said his thoughts were with "our compatriots in Mayotte, who have gone through the most horrific few hours and who have, for some, lost everything, lost their lives".
While some French aid and rescue workers have reached Mayotte, efforts to get to some communities are still under way.
Francois-Xavier Bieuville, the island's prefect, told local media the death toll could rise significantly once the damage was fully assessed. He warned it would "definitely be several hundred" and could reach the thousands.
French Interior Minister Bruno Retailleau, who is scheduled to visit the island to assess the damage and co-ordinate further relief efforts, acknowledged the "exceptional severity" of the cyclone and assured that efforts to assist the population were being ramped up.
Cyclone Chido also made landfall in Mozambique, where it brought flash flooding, uprooted trees and damaged buildings about 25 miles (40km) south of the northern city of Pemba.
The cyclone caused structural damage and power outages in the northern coastal provinces of Nampula and Cabo Delgado on Saturday morning, local authorities reported.
Guy Taylor, a spokesperson for aid agency Unicef in Mozambique, said, "we were hit very hard in the early hours of this morning".
"Many houses were destroyed or seriously damaged, and healthcare facilities and schools are out of action," he added.
Mr Taylor said Unicef was concerned about "loss of access to critical services", including medical treatment, clean water and sanitation, and also "the spread of diseases like cholera and malaria".