Officials in Tonga began to survey the damage from Tropical Cyclone Gita Tuesday morning.
Home damage was widespread in the wake of the storm, according to emergency officials.
Emergencies have been declared in Tonga and American Samoa.
At least three people have been seriously injured.
As daybreak came Tuesday morning in Tonga, residents and officials began to survey the damage left behind by the powerful Tropical Cyclone Gita.
No deaths have been confirmed from the storm, but at least three people sustained serious injuries, 1NEWS reports.
In an interview with Radio New Zealand, Tonga National Emergency Office spokesman Graham Kenna said countless homes had been damaged by the storm when it hit Tonga, and officials had not yet been able to restore power and water service to its citizens. Most of the damage ranged from roofs blown away to fallen trees and flooding, Newshub reported.
"I've been involved in disaster responses for 30-plus years and it's the worst situation I have been in," Kenna told Radio New Zealand.
About 40 percent of the homes in the capital city of Nuku'alofa lost their roofs in the storm, an emergency management official told Sky News, as reported by Newshub. On the northern end of the city, near the coastline, Tonga's Parliament house was destroyed.
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New Zealand Minister of Foreign Affairs Winston Peters announced an initial aid fund will provide $540,000 for water, shelter and sanitation, according to 1NEWS.
"We stand ready to provide additional support as the extent of the damage becomes clear," Peters said in a statement obtained by 1NEWS. "Given the force of this Cyclone all signs point to a lengthy clean-up effort and our thoughts are with the Government and people of Tonga as they come to terms with the scale of this disaster."
"We are seeing shops that the rooftops have been uprooted all their goods are exposed. We are seeing floods and also a lot of branches and a lot of electric lines," Red Cross volunteer Victoria Helot told Radio New Zealand. "We have talked to some women this morning their priorities are water, blankets and food.
"It is a big issue because this is their livelihood and it is like we have to start all over again," she added. "You know there is no electricity, there is no water."
Crews planned to do an assessment of the damage, but roads were blocked by debris and downed trees and power lines, according to Radio New Zealand. Officials say their assessment may have to wait until tomorrow morning.
The eye of Gita passed just south of the low-lying Tongatapu group of islands in southern Tonga Monday night local time with maximum sustained winds estimated at 145 mph, according to the U.S. Joint Typhoon Warning Center. Tonga is 18 hours ahead of U.S. Eastern Daylight Time.
From midnight to about 2 a.m. local time Tuesday morning, conditions were at their worst, and in Nuku'alofa, residents remained hunkered down in structures they hoped would survive the storm.
"Very frightening, we tried to tell ourselves we were fine but we were not, you know," Virginie Dourlet told 1NEWS. "I guess we were mostly concerned about the roof but actually we were concerned for all the wrong reasons."
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As the storm raged overnight, hundreds of residents called the emergency office for help, Kenna also told Radio New Zealand.
A state of emergency was declared in Tonga by acting prime minister Semisi Sika because of the storm, and shelters were opened to house evacuees, according to the Guardian. The nation of 107,000 residents consists of more than 100 islands, but a majority of the population lives on Tongatapu Island, which was battered by the storm.
"It's screaming like a freight train and it just keeps getting noisier and noisier," 1NEWS reporter Barbara Dreaver told the station while she sheltered in a hotel room in Nuku'alofa. "Compared to storms at home (in New Zealand), this just doesn't compare. It's like someone screaming out of control, the palm trees are bent over sideways, there's a lot of variables in play. You're completely at its mercy."
The storm's track raked the northern eyewall across the Tongan islands of Tongatapu and 'Enu. Power was switched off in parts of Tonga, and the Tonga Meteorological and Coast Radio Services office in Fua'amotu sustained damage, forcing the office to hand off forecasting duties to Fijian meteorologists, 1NEWS reported Tuesday morning.
Commissioner of Tonga Police Stephen Caldwell ordered a curfew in Nuku'alofa from 9 p.m. Monday until 7 a.m. Tuesday, according to Matangi Tonga Online. Tourists were advised to not travel to Tonga until the storm passed, the New Zealand Herald reported.
"We are urging people to seek refuge from this severe cyclone that could be the most powerful in the country's history," said Commissioner Caldwell.
In New Zealand, Kiwis awaited news from friends and family in Tonga, and by Tuesday morning, they were growing more desperate to get any news from the islands. Wellington resident Nastajia Bourke said her sister was riding out the storm by herself in her home, and she lost contact late Monday night.
"The last we heard was her saying the roof was starting to lift, that water was coming in through her roof and the front door, which must have blown open," she told Stuff New Zealand.
According to the Fiji Meteorological Service, Gita's central pressure was estimated at 930 millibars late Monday night, stronger than Hurricane Harvey when it made landfall along the Texas coast in late August 2017.
According to NOAA's historical hurricane tracks, only one other Category 4 tropical cyclone had passed within 200 nautical miles of Nuku'alofa in modern records, January 2014's Cyclone Ian.
Ian hit the Ha'apai islands of Tonga hardest but passed east of the most heavily populated island of Tongatapu.
Gita is now forecast to pass well south of Fiji's largest islands, including its capital city, Suva. Still, some bands of rain containing gusty winds could affect that nation, particularly in the smaller southernmost islands.
Gita previously caused damage in the South Pacific after brushing Samoa and American Samoa late last week with flooding rain and damaging winds.
In American Samoa, officials have begun a full assessment of the damage from the storm, the Associated Press reported. Public schools have been shut down for the week.
The damage to homes and utilities in the U.S. territory prompted President Donald Trump to declare a state of emergency Sunday evening.