(CNN) Relief workers reported "unbelievable destruction" after Tropical Cyclone Pam smashed the capital of Vanuatu, the Australian Red Cross said Saturday.

The Australian Red Cross said via Twitter that "humanitarian needs will be enormous. Many people have lost their homes. Shelter, food and water (are) urgent priorities" in Port Vila.

Meteorologists said the storm has weakened some, but it was still pounding the islands after hours of fierce winds and torrential rain.

"#CyclonePam still tearing through #Vanuatu. 'Much bigger than expected,' says our colleague in Port Vila. Initial reports of devastation," the Australian branch of UNICEF said on Twitter earlier.

Pam, one of the strongest storms seen in the South Pacific in years, earlier made a direct hit on the capital, raising fears of mass destruction.

#CyclonePam still tearing through #Vanuatu. "Much bigger than expected," says our colleague in Port Vila. Initial reports of devastation — UNICEF Australia (@unicefaustralia) March 13, 2015

In its 8 a.m. Saturday update, the Vanuatu Meteorological Services warned of "very destructive hurricane force winds" of 155 mph (250 kilometers per hour) in Shefa and Tafea provinces, with several others facing "very rough to phenomenal seas with heavy swells."

The Joint Typhoon Warning Center in Pearl Harbor, Hawaii, said the cyclone had weakened from the equivalent of a Category 5 hurricane to a Category 4. It has dumped more than 9 inches of rain on the capital in a 36-hour period and has wind gusts of up to 190 mph (305 kph).

Pam is forecast to move southeastward along the western edge of the southern islands of Vanuatu. It isn't expected to make any additional landfalls before dissipating.

It will continue to weaken as it crosses cooler waters and encounters higher wind shear.

Pam is expected to pass east of New Zealand on Sunday and into Monday. It could bring heavy rainfall to North Island, including Auckland.

The capital, the biggest city in the Vanuatu island chain, sits on the coastline, which is vulnerable to storm surges during powerful cyclones.

Tropical Cyclone Pam is the strongest storm to make landfall since the devastating Super Typhoon Haiyan hit the Philippines in 2013.

Photos: Tropical Cyclone Pam hits Vanuatu Photos: Tropical Cyclone Pam hits Vanuatu A woman sits on a fallen tree among what's left of her garden in Port Vila, Vanuatu, on Thursday, March 19, nearly a week after Cyclone Pam ripped through the island nation in the South Pacific. Vanuatu President Baldwin Lonsdale has called the storm a "monster," saying it has set back the development of his country, already one of the poorest in the region, by years. Hide Caption 1 of 34 Photos: Tropical Cyclone Pam hits Vanuatu A young boy plays on a destroyed banana plantation in Mele, Vanuatu, on March 19. Hide Caption 2 of 34 Photos: Tropical Cyclone Pam hits Vanuatu A nun surveys the damage near Port Vila on March 19. Hide Caption 3 of 34 Photos: Tropical Cyclone Pam hits Vanuatu People put clothes out to dry near Port Vila on March 19. Hide Caption 4 of 34 Photos: Tropical Cyclone Pam hits Vanuatu An aid worker treats an injured woman on Tanna Island on Wednesday, March 18. Hide Caption 5 of 34 Photos: Tropical Cyclone Pam hits Vanuatu A child walks through a damaged classroom on Tanna Island on March 19. Hide Caption 6 of 34 Photos: Tropical Cyclone Pam hits Vanuatu Mercy Watskal holds her week-old granddaughter, Angelina, at the Enima Evacuation Center on Tanna Island on March 19. Hide Caption 7 of 34 Photos: Tropical Cyclone Pam hits Vanuatu Young men take apart a damaged hut on March 19 on Tanna Island. Hide Caption 8 of 34 Photos: Tropical Cyclone Pam hits Vanuatu Australian doctors help a young girl on the Vanuatu island of Tanna on Wednesday, March 18. Hide Caption 9 of 34 Photos: Tropical Cyclone Pam hits Vanuatu A man stands under the damaged rooftop of a school in Vanuatu's capital, Port Vila, on March 18. Hide Caption 10 of 34 Photos: Tropical Cyclone Pam hits Vanuatu Books recovered from a school are left out to dry in Port Vila on March 18. Hide Caption 11 of 34 Photos: Tropical Cyclone Pam hits Vanuatu A ship sits beached along the shore of Tanna on March 18. Hide Caption 12 of 34 Photos: Tropical Cyclone Pam hits Vanuatu An Australian army relief aircraft arrives with supplies at the airport in Tanna on March 18. Hide Caption 13 of 34 Photos: Tropical Cyclone Pam hits Vanuatu Residents clean up debris in Port Vila on Tuesday, March 17. Hide Caption 14 of 34 Photos: Tropical Cyclone Pam hits Vanuatu Children play on March 17 in water among fallen trees near Port Vila. Hide Caption 15 of 34 Photos: Tropical Cyclone Pam hits Vanuatu Aid is on board a Royal Australian Air Force C-17 Globemaster transport aircraft headed to Port Vila on Monday, March 16. Hide Caption 16 of 34 Photos: Tropical Cyclone Pam hits Vanuatu Debris from the cyclone is scattered in an area near Port Vila on March 16. Hide Caption 17 of 34 Photos: Tropical Cyclone Pam hits Vanuatu A boy kicks a ball through the ruins of his family home as his father picks through debris on March 16. Hide Caption 18 of 34 Photos: Tropical Cyclone Pam hits Vanuatu A bridge and road that suffered dramatic damage from Cyclone Pam are seen outside Port Vila, the capital of Vanuatu, on Sunday, March 15. Hide Caption 19 of 34 Photos: Tropical Cyclone Pam hits Vanuatu A resident stands in her badly damaged home outside Port Vila on March 15. Hide Caption 20 of 34 Photos: Tropical Cyclone Pam hits Vanuatu An aerial photo taken by CARE Australia on March 15 shows the widespread damage caused by the cyclone in Vanuatu. Hide Caption 21 of 34 Photos: Tropical Cyclone Pam hits Vanuatu A resident clears mud and other debris outside homes near Port Vila on March 15. Hide Caption 22 of 34 Photos: Tropical Cyclone Pam hits Vanuatu Residents work amid the debris left by the cyclone outside Port Vila on March 15. Hide Caption 23 of 34 Photos: Tropical Cyclone Pam hits Vanuatu Locals walk past debris in Port Vila on March 15. Hide Caption 24 of 34 Photos: Tropical Cyclone Pam hits Vanuatu People walk past debris scattered on a street in Port Vila, Vanuatu, on Saturday, March 14. Hide Caption 25 of 34 Photos: Tropical Cyclone Pam hits Vanuatu Damaged boats are seen on Saturday, March 14, in Port Vila, Vanuatu's capital. Hide Caption 26 of 34 Photos: Tropical Cyclone Pam hits Vanuatu Surf pounds the shore as people walk among debris scattered by Cyclone Pam in Port Vila, Vanuatu, March 14. Hide Caption 27 of 34 Photos: Tropical Cyclone Pam hits Vanuatu Residents look through storm damage in Port Villa on March 14. Hide Caption 28 of 34 Photos: Tropical Cyclone Pam hits Vanuatu People move away from the beach March 13 on the island of Kiribati. Hide Caption 29 of 34 Photos: Tropical Cyclone Pam hits Vanuatu A person walks past flooding near Port Vila on March 13. Hide Caption 30 of 34 Photos: Tropical Cyclone Pam hits Vanuatu Strong winds blow trees as Pam hits Vanuatu on March 13. Hide Caption 31 of 34 Photos: Tropical Cyclone Pam hits Vanuatu Shops are boarded up in Port Vila on Thursday, March 12. Hide Caption 32 of 34 Photos: Tropical Cyclone Pam hits Vanuatu Preparations are made in Port Vila ahead of the storm on March 12. Hide Caption 33 of 34 Photos: Tropical Cyclone Pam hits Vanuatu People in Port Vila buy supplies ahead of the storm on March 12. Hide Caption 34 of 34

Chloe Morrison, an emergency communications director for the humanitarian organization World Vision, told CNN that she could see some light between her boarded-up windows but it was still hard to see the totality of the destruction outside the house where she and seven others huddled in a back room during the storm.

"Seven hours hunkered down and it's still not safe to go outside," she said. "The winds are still really howling. We're really lucky to be in a concrete house."

Part of the tin roof twisted off the house and landed by one of the windows, she said. She also noted that two trees outside didn't get uprooted, but they had not one bit of fruit or any leaves remaining.

Despite the "quite terrifying ordeal," Morrison said, their house didn't have any damage.

Through the night, the wind and torrential rain made it sound like an angry ocean was just outside their doors, she said.

World Vision, which says it's been based in Vanuatu for more than 30 years, said its emergency assessment team would head out to view the damage when it is safe.

The staff helped prepare communities on the islands for the cyclone by positioning water, food, blankets, tarpaulins, and shelter, hygiene and kitchen kits in key places, it said, as well as advising on disaster preparedness.

Residents have been advised to seek shelter in places such as churches, universities and schools.

"The strongest thing they've got is cement churches," said Inga Mepham, program director for CARE International for the Vanuatu program. "Some of them don't have that. It's hard to find a structure that you'd think would be able to withstand a Category 5 (storm)."

'Vanuatu Monster'

Earlier, photographer Michael McLennan -- who said the storm is being called the "Vanuatu Monster" -- told CNN that the "strength of winds is incredible."

Video footage he shot earlier Friday showed palm trees being whipped by wind and rain.

Cyclone Pam's projected path

Evacuation alerts have been issued for several parts of the country.

Even before the sun rose Saturday, Vanuatu was already getting hit hard, with most communication and power cut off due to the storm.

"The wind outside is terrifying," Michael Wolfe, World Vision's national director in Vanuatu, told that organization. "I can't imagine what it's like for families out there who weren't able to find safe shelter before the storm."

The archipelago nation northeast of Australia contains 83 small islands, many of which have little infrastructure and lack the strong housing structures that can endure a walloping storm.

Because of the tropical climate in Vanuatu, some of the housing is made of lighter building materials, including straw and corrugated metals.

Residents prepared for the storm, boarding up windows and chopping down trees that stand close to buildings in case they could become debris or cause further damage or injury.

CNN host Bill Weir, who was recently in Vanuatu on assignment, said that while Port Vila has some modern development in the form of an airport, large hotels and a convention center that's under construction, life on some of the islands has remained almost unchanged for thousands of years.

"For search and rescue, for bringing food and supplies and medicine, it's extremely challenging," he said.

Pam has triggered watches and warnings in the Solomon Islands and New Zealand.