Cyclone Harold

A satellite image shows Harold slamming Vanuatu on Monday

In Vanuatu, homes have been destroyed and livelihoods ruined by Tropical Cyclone Harold, which passed through the country's northern islands as a category-five system, wreaking devastation.

The total scale of the destruction is not yet clear as main communication lines to the hardest hit islands of the archipelago nation have been severed.

But pictures from Espiritu Santo and Malo Islands show villages reduced to ruins by the storm, which reportedly carried 235km/h winds, overnight.

Save The Children, which has staff in Santo and the capital Port Vila, believe the eye of the monster system travelled directly over Luganville, the country's second biggest settlement, with 17,000 people.

'We expect over 20,000 children have been impacted by the cyclone,' country director Luke Ebbs told AAP.

There is now an anxious wait for communications to be restored, or weather conditions to calm down to allow travel to the hardest-hit regions.

'Presumably it's caused a huge amount of damage but we just don't know how much,' Mr Ebbs said.

'We and other agencies are struggling to get information about the situation on the ground.

'The eye of the storm passed over Luganville. We can imagine the damage to infrastructure, buildings, livelihoods, houses is significant.

'Our first priority will be checking on the safety of our staff in Santo and then trying to get a picture of the immediate needs that have emerged.

'We are worried that children and families across these islands have been through a terrifying experience and there will be immediate needs emerging for psychosocial support to those affected, nutritious food, safe water and safe housing.'

Mr Ebbs said the Vanuatu's government is 'well experienced in leading responses to cyclones and we stand ready to support them as we have in previous years'.

Radio NZ reports that houses have collapsed, roads have flooded, the coastline has been battered.

There are yet to be any reports of loss of life.

Harold is the most brutal cyclone to hit the South Pacific in at least two years.

The storm remains as a category-five system, the highest classification, and has moved east of Vanuatu.

It will reach Fiji in the next 72 hours if it continues on its current direction and speed.