Australia’s minister for the Pacific, Zed Seselja, says initial reports suggest no mass casualties in Tonga following the eruption of a volcano that triggered a tsunami, but Australian police have visited beaches with significant damage and “houses thrown around”.

Australia and New Zealand sent surveillance flights on Monday to assess the damage after Tonga was isolated from the rest of the world when Saturday’s eruption blanketed the Pacific Island with ash.

The flights, along with detailed pictures and video, were due back in Australia and New Zealand on Monday evening.

“We know there is some significant damage, and know there is significant damage to resorts,” Seselja said in an interview with an Australian radio station, adding Tonga’s airport appeared to be in relatively good condition.

One British woman was reported missing, he said. The surveillance flights assessed the situation in outer islands where communication was completely cut off.

Seselja told ABC TV there were “no reports of mass casualties”.

Tonga’s deputy head of mission in Australia, Curtis Tu’ihalangingie, asked for patience as Tonga’s government decided its priorities for aid.

Tonga is concerned about the risk of aid deliveries spreading Covid to the island which is free of the virus.

“We don’t want to bring in another wave – a tsunami of Covid-19,” Tu’ihalangingie said by telephone. “When people see such a huge explosion they want to help.”

But, he said, Tonga diplomats were concerned by some private fundraising efforts and he urged the public to wait until a disaster relief fund was announced.

Any aid sent to Tonga would need to be quarantined, and it was likely no foreign personnel would be allowed to disembark aircraft, the diplomat said.

The eruption of the Hunga-Tonga-Hunga-Ha’apai volcano triggered a tsunami on the shores of Tonga and cut off phone and internet lines for the entire island. International communication was severely hampered by damage to an undersea cable, which could take more than a week to restore, and Australia and New Zealand were assisting with satellite calls.

Telephone networks in Tonga have been restored but ash was posing a major health concern, contaminating drinking water. “Most people are not aware the ash is toxic and bad for them to breathe and they have to wear a mask,” Tu’ihalangingie said.

The New Zealand prime minister, Jacinda Ardern, said boulders and boats had washed ashore on Tongatapu, Tonga’s largest island and home to the capital, about 65km south of the volcano.

“Seeing some of those waves come in and peeling back fencelines and structures, you can see the force of those surges,” she said. “Everyone just wants to establish how wide scale that impact has been … we want to be in Tonga and on the ground as soon as we are possibly able to be.”

Completely destroyed

The Ha’atafu Beach Resort, on the Hihifo peninsula, 21km (13 miles) west of the capital Nuku’alofa, was “completely wiped out”, the owners said on Facebook.

The family that manages the resort had run for their lives through the bush to escape the tsunami, it said.

“The whole western coastline has been completely destroyed along with Kanukupolu village,” the resort said.

British woman Angela Glover was missing after she was washed away by a wave when she and her husband, James, who own the Happy Sailor Tattoo in Nuku’alofa, had gone to get their dogs.

The husband managed to hold onto a tree but his wife, who runs a dog rescue shelter, and their dogs were swept away, New Zealand state broadcaster TVNZ reported.

The Red Cross said it was mobilising its network to respond to what it called the worst volcanic eruption the Pacific had experienced in decades.

Katie Greenwood, the Pacific head of delegation for the International Federation of Red Cross and Red Crescent Societies, said up to 80,000 people could have been affected by the tsunami.

Hunga-Tonga-Hunga-Ha’apai has erupted regularly over the past few decades but the impact of Saturday’s eruption was felt as far away as Fiji, New Zealand, the United States and Japan.

Two people drowned off a beach in northern Peru due to high waves caused by the tsunami.

More than a day after the eruption, countries thousands of kilometres to the west have volcanic ash clouds over them, New Zealand forecaster WeatherWatch said.

Early data suggests the eruption was the biggest blast since Mount Pinatubo in the Philippines 30 years ago, New Zealand-based volcanologist Shane Cronin told Radio New Zealand. “This is an eruption best witnessed from space,” Cronin said.