The official death toll from a massive cyclone that tore through Vanuatu has risen to four, with fears it could jump significantly, officials from the tiny South Pacific archipelago said Monday.

Officials had still not made contact with outlying islands and were struggling to determine the scale of devastation from Cyclone Pam, which tore through Vanuatu early Saturday, packing winds of 270 kilometers (168 miles) per hour.

Paolo Malatu, coordinator for the National Disaster Management Office, said two people had been confirmed dead in the capital, Port Vila, and two more on the southern island of Tanna. He said another 20 people had been injured.

With power lines and phone circuits down, officials have no way of knowing the scope of the damage and injuries on the hard-hit outer islands. Malatu said officials had dispatched every plane and helicopter they could Monday to fly over the islands and identify those hardest hit.

"The damage to homes and infrastructure is severe," he said. "The priority at the moment is to get people water, food and shelter."

He said there was major damage to many government buildings, and bridges were down outside the capital, making travel by vehicle impossible even around the main island of Efate.

Vanuatu has a population of 267,000 people spread over 65 islands. About 47,000 people live in the capital.

Telephone networks are notoriously spotty in South Pacific island nations such as Vanuatu, particularly after storms. It often takes days before networks can be restored. Malatu said he hoped service would be restored in the next few days.

Australia and New Zealand have sent in relief supplies. Port Vila's airport was damaged by the storm and temporarily closed to commercial flights, but the first delivery of supplies arrived Sunday from the Red Cross, Malatu said.

"People are really upset and it's really hard, just because for the last couple of years, we haven't received a really big cyclone like this one," said Isso Nihmei, Vanuatu coordinator for the environmental and crisis response group 350. "Most people right now, they are really homeless."

He came upon one of the storm's victims on Saturday while surveying the damage along the coastline with other relief workers. The group spotted a man lying on the ground, not breathing, and rushed him to the hospital. By the time they arrived, however, he was dead, Nihmei said.

Structural damage across Port Vila was extensive, Nihmei said, with the majority of homes severely damaged or destroyed.

Hannington Alatoa, head of the Vanuatu Red Cross Society, said flyovers by New Zealand and Australian relief teams showed much of the country had been "flattened." At least half of the population, or about 130,000 people, has been affected, Alatoa said in Sendai, Japan, where he and other Vanuatu officials were attending a U.N. conference on disaster risk reduction.

"No trees, no foliage, no iron structures standing on the western part of Tanna," Alatoa said. "Trees blocked the roads. ... People are in great need of water."

Alatoa said he has been unable to contact his family.

"I tried yesterday to call them from my hotel room, but I didn't get through," he said. "It's difficult. I'm praying that they are able to cope with the situation they have on the ground right now."

Vanuatu's president, Baldwin Lonsdale, who was also attending the conference in Sendai, appealed for international support.

He said authorities would have a better idea of the extent of the damage and casualties on the outer islands once they reached them on Monday. "However, I can say from past experience that there will be severe damage to schools, health facilities, roads and public utilities," he said in a statement, calling the cyclone a "major calamity for our country."

Many people who have ventured out from 23 emergency shelters around Port Vila have found their homes damaged or blown away altogether, said Chloe Morrison, a World Vision emergency communications officer. Teetering trees and downed power lines have made parts of the capital hazardous.

She said communications have been so problematic that her aid group hasn't yet been able to account for many of its own 76 staff members on the islands.

For anybody who wasn't in a secure shelter during the cyclone "it would have been a very, very tough time for them," she said.

UNICEF estimated that 54,000 children were among those affected by the cyclone.

The small island nation, located about a quarter of the way from Australia to Hawaii, 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.

Scientists say it's impossible to attribute single weather events like Cyclone Pam to climate change.

The cyclone has already caused damage to other Pacific islands, including Kiribati and the Solomon Islands. Some homes were evacuated in New Zealand Monday to escape flooding as the weakening storm moved past the North Island's East Cape region.