Australian sailors will embark on a Christmas eve humanitarian mission to help thousands of people in cyclone-struck Fiji.

HMAS Adelaide will leave Brisbane on Thursday as the federal government provides $4.5 million to help the island neighbour recover from category-five Tropical Cyclone Yasa.

The system was one of the strongest cyclones recorded in the Pacific, and made landfall on the northern island of Vanua Leva last week.

It brought torrential rain and gusts up to 345km/h to the archipelago, which was already ravaged by Tropical Cyclone Harold in April.

The homes of thousands of Fijians, along with schools and other infrastructure were damaged or destroyed.

At least four people were killed.

On Kia Island and across the North, severe #TCYasa has opened a painful window to the climate reality.

These Fijians feel the urgency of action like few others. But this is not Fiji's climate emergency alone — it is the world's, and only a global response will suffice. pic.twitter.com/00uK65YCav

— Aiyaz Sayed-Khaiyum (@AiyazSKFiji) December 23, 2020

HMAS Adelaide will carry personnel and equipment to complement the efforts of the Fijian government, Defence Minister Linda Reynolds said.

“Members from the Australian Army’s 6th Engineering Support Regiment from Brisbane will assist Fijian authorities to clear debris, and repair critical infrastructure and schools,” she added.

The ship with a crew of about 400 is expected to arrive in Fiji next week.

The relief package will include supplies such as building materials, tents, medical supplies, solar lighting and hygiene kits, education supplies and support for organisations and the Fiji Red Cross to aid their work with affected communities.

HMAS Adelaide will deploy to #Fiji to provide immediate assistance to thousands of Fijians whose homes, schools & other local infrastructure were damaged or destroyed by #TCYasa. Australia stands with our Fijian vuvale 🇦🇺🇫🇯 @Australian_Navy @deptdefence @MarisePayne @dfat @FijiPM pic.twitter.com/QLU0xeNEmy

— Linda Reynolds (@lindareynoldswa) December 23, 2020

In the immediate aftermath of the cyclone Australia sent emergency humanitarian supplies to Fiji on two RAAF C-17A Globemaster flights.

The RAAF also conducted two aerial assessment missions to obtain an early picture of the scale of damage caused by Yasa in remote locations.

Aerial assessment showed that Bua province on the northern island of Vanua Levu suffered 70 per cent damage and destruction, while the small island of Kia was completely destroyed, Fiji Red Cross Director General Ilisapeci Rokotunidau said.

“It’s like a ground zero, there’s nothing left,” Ms Rokotunidau told Reuters.

Today we have 2 maritime assets supporting @FijiNDMO @FijiRedCross delivering relief & rations to islands off the coast of Vanua Levu and 3 aircraft on standby for urgent movements with our global partner @YachtAidGlobal #TCYasa @FijianGovt @UNOCHA_Pacific #SavingFijianLives pic.twitter.com/ZBi2aVCDKu

— Life Flight Fiji Trust (@LifeFlightFj) December 22, 2020

While the largest island of Viti Levu, where about three-quarters of Fijians live, was spared the worst, Vanua Levu and other small islands were in dire need of fresh water and shelter.

Disrupted communications and poor weather were hampering the damage assessment effort but Red Cross volunteers were assisting those in need, Ms Rokotunidau said.

There were concerns about the spread of diseases.

Foreign Affairs Minister Marise Payne said leftover aid sent to Fiji in the aftermath of Tropical Cyclone Harold in April was also used to help meet the immediate needs of those affected by Yasa.

-AAP