Three of Tonga’s smaller islands suffered serious damage from tsunami waves, officials said, as a wider picture emerges of the destruction caused by the eruption of an undersea volcano near the Pacific archipelago nation.

Communications have been down throughout Tonga since the eruption on Saturday, but a ship made it to the outlying islands of Nomuka, Mango and Fonoifua on Wednesday, and reported back that few homes remain standing after settlements were hit by 49ft-high waves, Red Cross official Katie Greenwood said.

She told the AP from Fiji: “Very unfortunate information has come to light overnight about the three islands that we were really worried about – that they have all suffered devastating consequences as an effect of these incoming waves.

“Most of the structures and dwellings on those islands have been completely destroyed.”

It is not clear yet what assistance Tonga needs or wants from the international community.

Complicating matters is the country’s concern over the possible spread of Covid-19, which it has effectively kept outside its borders except for one case reported in a traveller from New Zealand in October.

Tonga is hoping for “almost contactless disaster relief” as a precaution, Ms Greenwood said, acknowledging that this would complicate efforts but is also understandable amid the pandemic.

“They really don’t want to exchange one disaster for another,” she said.

In anticipation of the country’s needs, New Zealand has already sent two ships. One is carrying 250,000 litres (66,000 gallons) of water and a desalination plant with the capacity to produce 70,000 more litres (18,492 gallons) per day, and another is bringing a survey and diving team to help assess the damage to shipping channels, ports and wharf infrastructure.

New Zealand foreign minister Nanaia Mahuta said the teams would also be available to help if needed with the evacuation of the approximately 150 people who live on the devastated outlying islands.

“We stand ready to assist where it is useful to the government of Tonga, and where they are satisfied with Covid protocols,” she said.

Australia is also preparing to send aid by air and ship, and Prime Minister Scott Morrison said he expected to talk with his counterpart in Tonga later Wednesday to better understand what is needed.

“Our defence forces have stood up their operation and are deploying as necessary and directed,” he said. “So we feel deeply for our family in Tonga.”

The volcano coated the main island with a 2cm layer of ash, which has rendered the 2.6-kilometer (1.6 mile) runway at Fua’amotu International Airport unusable.

Volunteers have been working to sweep ash away to clear a path for aid planes to land, and there were hopes it may be ready as early as Thursday.

Communications have been severely restricted because the single underwater fibre-optic cable that connects Tonga to the rest of the world was likely severed in the eruption. The company that owns the cable said the repairs could take weeks.

Satellite images captured the spectacular eruption of the Hunga Tonga Hunga Ha’apai volcano, with a plume of ash, steam and gas rising like a giant mushroom above the South Pacific.

The volcano is located about 40 miles north of Tonga’s capital, Nuku’alofa.

The heavy amount of ash in the air has also meant that satellite communications have been sporadic but they are improving, Ms Greenwood said.

So far, it seems the country has avoided the widespread devastation that many initially feared.

The government said on Tuesday it has confirmed three deaths – two local residents and a British woman – though it has cautioned that the toll is expected to rise as more reports come in from outlying areas.

On Tonga’s main island of Tongatapu, perhaps the biggest problem is the ash that has transformed it into a grey moonscape, contaminating the rainwater that people normally rely on to drink.

Ms Greenwood said people had been warned in advance to protect their water supplies, and that clean drinking water remains the top need.

“Water is definitely, 100%, the top priority at this point in time, along with shelter needs,” she said.