Winds from an extremely powerful cyclone that blew through the Pacific's Vanuatu archipelago were beginning to subside Saturday, revealing widespread destruction and unconfirmed reports of dozens of deaths as relief workers rushed to assess the damage.

Chloe Morrison, a World Vision emergency communications officer who is in Port Vila, said the capital's streets were littered with roofs blown from homes, uprooted trees and downed power lines. She said she's hearing reports of entire villages being destroyed in more remote areas.

She said there is no power or running water in the capital and that communication remains unreliable.

"It's still really quite dangerous outside. Most people are still hunkering down," she said. "The damage is quite extensive in Port Vila but there are so many more vulnerable islands. I can't even imagine what it's like in those vulnerable communities."

U.N. Secretary General Ban Ki-moon said the impact and scope of the disaster caused by Cyclone Pam wasn't yet clear, but he feared the damage and destruction could be widespread.

"We hope the loss of life will be minimal," he said during a World Conference on Disaster Risk and Reduction in Japan. The U.N. said it was preparing to deploy emergency rapid response units.

The president of Vanuatu, Baldwin Lonsdale, who was attending the conference, told participants: "I do not really know what impact the cyclone has had on Vanuatu."

"I am speaking to you today with a heart that is so heavy," he said. "I stand to appeal on behalf of the government and the people to give a helping hand in this disaster."

Morrison said the winds seemed to peak between midnight and 1 a.m. Saturday. She said she was in a fully boarded-up cyclone-proof house but still spent a frightening night as a tree and a tin roof from a nearby home hit her house.

A westward change of course put populated areas directly in the path of Cyclone Pam's 270 kilometer (168 mile) -per-hour winds. The U.N. Office for the Coordination of Humanitarian Affairs said there were unconfirmed reports of deaths in Vanuatu's northeastern islands after Cyclone Pam moved off its expected track.

Australia was preparing to send a crisis response team to Vanuatu if needed, Australian Foreign Minister Julie Bishop said.

"There are destructive winds, rain, flooding, landslides, sea surges and very rough seas and the storm is exceedingly destructive there," she said. "We are still assessing the situation, but we stand ready to assist."

Located about a quarter of the way from Australia to Hawaii, Vanuatu has a population of 267,000 spread over 65 islands. About 47,000 people live in the capital.

The tiny Pacific island nation has repeatedly warned it is already suffering devastating effects from climate change with the island's coastal areas being washed away, forcing resettlement to higher ground and smaller yields on traditional crops.

The cyclone has already destroyed some homes and caused damage to other Pacific islands including Kiribati and the Solomon Islands.

David Gibson, acting director of the Vanuatu meteorology and geo-hazards department, said the winds could cause severe damage to the nation's buildings.

Alice Clements, a spokeswoman for relief agency UNICEF who is in Port Vila, said Friday the capital was like a ghost town as people took shelter. She said the pelting rain was blown horizontally by the wind.

Authorities in New Zealand are preparing for the storm, which is forecast to pass north of the country on Sunday and Monday.

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Associated Press writer Elaine Kurtenbach in Sendai, Japan, contributed to this report.