SYDNEY — Rescue workers began a massive relief operation in Vanuatu on Sunday following a devastating cyclone that killed at least six people, sent thousands into emergency shelters and disrupted communications in the Pacific island nation.

A nine-member U.N. team was due to arrive on Sunday to carry out an initial assessment of the damage from the category 5 cyclone named Pam, which at its peak covered the entire country on satellite maps and brought houses crashing down with winds of more than 185 miles per hour.

Several other neighboring countries also were affected.

Officials said the airport in Vanuatu’s capital, Port Vila, remained closed, though they hoped it might partly reopen later on Sunday to allow in the first relief planes.

As Cyclone Pam finally moved off to the southeast, more people left homeless by the disaster flooded into evacuation centers filled with thousands of evacuees, government officials said.

Fears remained high that outlying islands, where there are few support services, may have been especially hard hit by flash flooding and cyclone-related damage. Officials said they were still unable to contact any region outside the capital.

“Our communication link is still down,” Paolo Malatu, an official at the country’s National Disaster Management Office, told Reuters. “We have not got any information from outside Port Vila.”

“The biggest need at the moment is shelter and food and wash kits,” Malatu said.

“While it is too early to say for certain, early reports are indicating that this weather disaster could potentially be one of the worst in Pacific history,” UNICEF New Zealand Executive Director Vivien Maidaborn told Fox News.

With President Baldwin Lonsdale at a conference in Japan and unable to fly into Vanuatu, the government was being led temporarily by Charlot Salwai, acting minister for climate change, government officials said.

Officials on Sunday confirmed six fatalities, a toll that is expected to increase amid unconfirmed reports of dozens of dead in the nation’s remote northeast region. At least 20 others were injured.

“We anticipate that (death toll) will go higher, particularly as information comes from the remote islands. We are talking about islands that are remote and really small, with none of what we would call modern infrastructure,” said Colin Collett van Rooyen, Oxfam’s country manager in Vanuatu.

He added that the government had declared a state of emergency for Shefa province, where Port Vila is located, adding that he anticipated it would eventually be extended to the entire nation.

Formerly known as the New Hebrides, Vanuatu is a collection of around 83 islands with a population of 260,000. It experiences frequent earthquakes and storms, and aid officials regard it as one of the world’s poorest nations.

Aid agencies in nearby Australia and New Zealand were preparing to send help.