All schools in Vanuatu have been destroyed or damaged by Tropical Cyclone Pam, the United Nations says.

Aid agencies said conditions in cyclone-ravaged Vanuatu are among the most challenging they have ever faced with the severe storm tearing through the island nation, wiping out villages and displacing thousands.

At least eight people have been confirmed dead and more than 30 people injured after category five Pam tore through on Friday night packing wind gusts of up to 320 kilometres per hour.

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Aid workers have said they expect the death toll to rise as more information comes in from the nation’s 65 inhabited islands.

The United Nation’s Children’s Fund (UNICEF) said it would set-up safe spaces for children to continue with their basic education but said around 17,000 children under the age of five were at risk of poor health and malnutrition after the disaster.

“Children unable to attend school are vulnerable. Children need psychosocial support following the cyclone and its aftermath,” UNICEF said in a statement.

UNICEF said it was also working with Vanuatu’s government on water and sanitation and had begun distributing supplies to affected areas.

Vanuatu’s Red Cross said more than half of Vanuatu’s population is likely to have been affected by Pam.

“Personally I think that there will be a lot more [people affected] because the whole country was flattened,” the Red Cross’s Hannington Alatoa said.

More than half of Vanuatu’s population is likely to have been affected by Pam. Photo: Getty

Aid organisation CARE has estimated that 85 per cent of all houses in Port Vila have been destroyed.

It said the main water tanks in the capital Port Vila were empty and the city’s power supply had been damaged.

UNICEF said health centres, including the main hospital, had been damaged and patients had been moved to a new outpatient area.

Red Cross Vanuatu chief executive Jacqueline de Gaillarde said shops were already low on supplies because people had stockpiled food before the storm but those supplies were then lost when homes were destroyed.

Meanwhile, the country’s biggest mobile phone company Digicel said it had restored its network in the capital.

It said its technicians would now focus on the other main population centres like the rest of Efate island, Tanna and Santo.

Fears for Vanuatu’s isolated island communities

Authorities in Vanuatu are still struggling to establish contact with outer islands that bore the brunt of Pam’s winds.

The southern island of Tanna, about 200 kilometres south of Port Vila, with its 29,000 inhabitants took the full force of the storm.

Initial reports from aid groups said it had been devastated, along with the main town on the southern island of Erromango, with at least two people reported dead.

Aurelia Balpe, head of the Pacific office of the International Federation of Red Cross and Red Crescent Societies, said it appeared Tanna had suffered widespread damage.

Flood waters have moved inland following a storm surge on the island of Kiribati. Photo: Getty

She said a local Red Cross volunteer had been “traumatised” by the cyclone’s intensity.

“He sounded like he was in shock and we couldn’t get very much information from him, just that there was devastation,” Ms Balpe said.

Save the Children’s Vanuatu director Tom Skirrow said that aid agencies were preparing supplies but it would likely be three days before airfields in remote islands were cleared.

“We’ve had aerial surveillance … all we can tell is what we suspected, that everything’s destroyed, but we don’t know what’s happening with the people right now,” Mr Skirrow said.

Relief flights have begun arriving in the battered Port Vila and a clean-up is underway.

But workers on the ground said there was no way to distribute desperately needed supplies across the archipelago.

“Things in Port Vila are improving, people are returning to the market and getting on with the job of starting the clean-up,” said Tom Perry, from CARE Australia.

“But the key thing is we still have no contact with other provinces.

“That’s of grave concern because there’s no real sense from anyone of what the impact has been but we know in the south in particular, it sat under the eye of the storm for hours. It’s not going to be good, there’s no question.”

Tourists depart cyclone-devastated island

The first commercial flight from Vanuatu landed in Sydney on Monday carrying around 140 passengers, many of whom were greeted by relieved friends and family.

Bec Kerr, a tourist returning from Port Villa, said she was very well taken care of and was grateful to Vanuatuans.

“It was terrible there but people are just getting on with life and fixing everything up,” Ms Kerr said.

“It’s just unbelievable. People have got nowhere to live. Nowhere to sleep tonight.”

Australia has pledged $5 million in assistance to the Pacific nation and several military aircraft have been sent to help the international recovery mission.