Most of the homes on three of Tonga’s smaller islands have been “completely destroyed” by the tsunami that followed Saturday’s undersea volcanic eruption, the Red Cross has said.
With communications down, a ship made it to Nomuka, Mango and Fonoifua on Wednesday, an official said.
Few homes are said to remain standing after settlements were hit by 15m (49ft) waves.
“Very unfortunate information has come to light overnight about the three islands that we were really worried about,” the Red Cross’s Katie Greenwood said.
“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.”
Images believed to be from the village of Kanokupolu, on the island of Tongatapu, show trees down and debris strewn across the ground.
Two New Zealand navy vessels are due to arrive in Tonga on Friday, carrying critical water supplies.
“Securing access to safe drinking water is a critical immediate priority as there is a mounting risk of diseases such as cholera and diarrhoea,” Ms Greenwood said.
At least three people have died in the disaster, including British woman Angela Glover.
At least a month to restore communication cable
Meanwhile, an undersea communication cable connecting Tonga to the rest of the world will take at least a month to fix, its owner said on Wednesday.
“The cables are actually around the volcanic zone,” said Samiuela Fonua, chairman of Tonga Cable Ltd.
“We don’t know whether they are intact or blown away or stuck somewhere underwater. We don’t know if it’s buried even deeper.”
A specialist ship is intending to embark from Port Moresby, the capital of Papua New Guinea, at the weekend, Mr Fonua added.
But it will take eight or nine days to reach Samoa to collect equipment, and it will be “lucky” if the job is done
within a month.
“It could be longer than that,” Mr Fonua said.
International phone service restored
Telecoms operator Digicel said it had restored international phone connectivity, but internet links come via the undersea cable.
Meanwhile, a British man living in Tonga told Sky News the sound of the volcano erupting was “like bombs going off around the place”.
Alistair Coldrick, who runs whale-watching tours on the island of Vava’u, said he and his family fled to higher ground after hearing the explosion.