PORT VILA, Vanuatu — Relief workers saw a flattened landscape and widespread destruction in Vanuatu’s outer islands Tuesday after struggling for days to reach the areas of the South Pacific nation hardest hit by a fierce cyclone.

Radio and telephone communications with the outer islands were just beginning to be restored, but remained incredibly patchy three days after Cyclone Pam hit.

Australian military planes that conducted aerial assessments found significant damage, particularly on Tanna Island, where it appears that more than 80 percent of homes and other buildings were partially or completely destroyed, Foreign Minister Julie Bishop said.

“We understand that the reconnaissance imagery shows widespread devastation,” Bishop said. “Not only buildings flattened — palm plantations, trees. It’s quite a devastating sight.”

Teams of aid workers and government officials carrying medical and sanitation supplies, water, food and shelter equipment managed to land on Tanna and neighboring Erromango Island on Tuesday afternoon, said Colin Collett van Rooyen, Vanuatu director for aid group Oxfam. The two islands were directly in the path of the storm, which packed winds of 270 kilometers (168 miles) per hour when it hit early Saturday.

The destruction on Tanna was significantly worse than in the nation’s capital of Port Vila, where Pam destroyed or damaged 90 percent of the buildings, said Tom Perry, spokesman for CARE Australia.

“The airport was badly damaged, the hospital was badly damaged but still functioning … there’s one doctor there at the moment,” he said. “It’s obviously a pretty trying situation.”

The U.N. Office for the Coordination of Humanitarian Affairs reported that 11 people were confirmed dead, including five on Tanna, lowering their earlier report of 24 casualties after realizing some of the victims had been counted more than once. Officials with the National Disaster Management Office said they had no accurate figures on how many were dead, and aid agencies reported varying numbers.

The confusion over how many died in the storm reflects the difficulty officials face as they try to deal with a disaster spread across many remote islands amid a near-total communications blackout.

“Vanuatu is a challenging place at the best of times, in the sense of getting around and logistics,” Perry said. “So a situation like this is pretty testing.”

Poor weather and communications issues have hampered relief workers efforts to reach the outer islands for days. A break in the weather on Tuesday gave them a chance to try again, though access remained difficult. Most of the islands have no airports and those that do have only small landing strips that are tricky for large supply planes to navigate.