Tropical Cyclone Pam has caused widespread devastation in Vanuatu in the South Pacific.
According to unconfirmed reports sourced to the UN, at least 44 people have been killed but the official death toll stands at four.
Relief organisations fear complete destruction of the Vanuatu capital Port Vila.
Other Pacific islands such as Kiribati and the Solomon Islands have also been battered.
Smashing into Vanuatu with winds of up to 270kmph, the storm has knocked out power lines and communications.
Incessant rain has caused flash floods and many areas remain cut off. Although the cyclone has weakened, fierce winds are continuing.
The Australian Red Cross said via Twitter: "Humanitarian needs will be enormous. Many people have lost their homes. Shelter, food and water (are) urgent priorities," adding that the storm has inflicted "unbelievable destruction".
"We heard some of the people who were living close. They were shouting and calling us. So once we went down there, we saw this guy who was already dead. There [were] other people on the other side, so we went down to rescue them but they were really weak. We got them to hospital but they died in half an hour," Isso Nihmei, Vanuatu coordinator of climate change organisation 350, was quoted as saying by ABC News.
"The immediate concern is for a very high death toll but also an enormous amount of destruction and devastation," Sune Gudnitz, regional director for the UN's Office for the Co-ordination for Humanitarian Assistance (UNOCHA), told Reuters.
Gudnitz went on to compare the Category 5 cyclone to the powerful Typhoon Haiyan, which ripped through the Philippines in 2013.
"Vanuatu is a very vulnerable place because of its location in the middle of the ocean. It is possible that there will be a death toll that could be high. I can't give any numbers. I think it is a well-grounded fear," Gudnitz said from Fiji, which is also in Pam's path.