Vanuatu's president has told the BBC many of his people are homeless after the "monster" cyclone that ravaged the Pacific island nation on Saturday.
His voice breaking, Baldwin Lonsdale said Cyclone Pam had destroyed most buildings in the capital Port Vila, including schools and clinics.
A state of emergency has been declared in the tiny state of 267,000 people, spread over 65 islands.
At least eight people are reported to have been killed.
However, it is feared the toll will rise sharply as rescuers reach outlying islands in the impoverished country.
Thousands of people spent a second night in shelters.
The category five storm, with winds of up to 300km/h (185mph), veered off its expected course and struck populated areas when it reached Vanuatu early on Saturday local time (+11 GMT).
The authorities in Vanuatu are struggling to gauge the extent of the damage across the country because communications are down and fallen power lines and trees have blocked roads.
Meanwhile, the first deliveries of aid have arrived on air force planes from New Zealand and Australia.
The UK, France, UN and European Union have also promised help.
'Moments of terror'
In a statement on Sunday, Oxfam Australia said up to 90% of housing in Port Vila had reportedly been seriously damaged.
"This is likely to be one of the worst disasters ever seen in the Pacific," said Oxfam's Colin Collet van Rooyen in Port Vila.
"The scale of humanitarian need will be enormous and the proud people of Vanuatu are going to need a lot of help to rebuild their homes and their lives."
Immediate priorities, he said, were providing shelter, clean water and sanitation.
There were "15-30 minutes of absolute terror" as the cyclone tore into the island, said Alice Clements, a spokesperson for UN children's agency Unicef.
A UN disaster assessment team is due to arrive in Vanuatu in the coming hours.
"It's devastation out there," said Carina Smith, a British doctor on holiday in Vanuatu at the time the cyclone struck.
"Buildings, trees, power lines are down. Water isn't running clean from taps any more so there's a concern about contamination," she told the BBC.
"I've been up at the hospital [on Sunday and Saturday] and there's severe damage to the hospital, which is the capital city hospital and a referral hospital for all the archipelago of islands - it's lost most of its roof and it's flooded."
President Lonsdale - who on Sunday was said to be trying to return home from a disaster risk conference he had been attending in Japan when the cyclone hit - earlier made an impassioned plea for international help.
"I am speaking to you today with a heart that is so heavy," he said.
"I stand to appeal on behalf of the government and the people to give a helping hand in this disaster."
The extent of the devastation is unlikely to be known for several days, said Tom Skirrow, Save the Children's Vanuatu country director.
Unconfirmed reports on Saturday said 44 people had died in Penama province in the north-east of Vanuatu, according to the UN's Office for the Co-ordination for Humanitarian Assistance (UNOCHA).
Pam had already caused major damage on other Pacific islands, including Kiribati and the Solomon Islands.
Tuvalu, a group of nine tiny islands north-east of Vanuatu, also declared a state of emergency after the cyclone caused flash floods there.