Thick ash on an airport runway is delaying aid deliveries to the Pacific island nation of Tonga where significant damage was being reported days after a huge undersea volcanic eruption and tsunami.

New Zealand’s military is sending much-needed drinking water and other supplies, but said the ash on the runway will delay the flight by at least a day.

A towering ash cloud since Saturday’s eruption had prevented earlier flights. New Zealand is also sending two navy ships to Tonga that will leave on Tuesday and pledged an initial 1 million New Zealand dollars (£500,000) towards recovery efforts.

Communications with Tonga have been extremely limited, but New Zealand and Australia sent military surveillance flights to assess the damage on Monday.

UN humanitarian officials and Tonga’s government “report significant infrastructural damage around Tongatapu,” UN spokesman Stephane Dujarric said.

“There has been no contact from the Ha’apai Group of islands, and we are particularly concerned about two small low-lying islands — Mango and Fonoi — following surveillance flights confirming substantial property damage.”

New Zealand’s High Commission in Tonga also reported “significant damage” along the western coast of the main island of Tongatapu, including to resorts and along the waterfront area.

Satellite images captured the spectacular eruption, with a plume of ash, steam and gas rising like a giant mushroom above the South Pacific.

Tsunami waves of about 80 centimeters (2.7 feet) crashed into Tonga’s shoreline, and crossed the Pacific, causing minor damage from New Zealand to Santa Cruz, California. The eruption set off a sonic boom that could be heard as far away as Alaska.

Two people drowned in Peru, which also reported an oil spill after waves moved a ship that was transferring oil at a refinery.

New Zealand’s Acting High Commissioner for Tonga, Peter Lund, said there were unconfirmed reports of up to three fatalities on Tonga so far.

One death has been confirmed by family: British woman Angela Glover, 50, who was swept away by a wave.

Nick Eleini said his sister’s body had been found and that her husband survived.

“I understand that this terrible accident came about as they tried to rescue their dogs,” Mr Eleini told Sky News. He said it had been his sister’s “life dream” to live in the South Pacific and “she loved her life there”.

The explosion of the Hunga Tonga Hunga Ha’apai volcano, about 64 kilometres (40 miles) north of Nuku’alofa, was the latest in a series of dramatic eruptions. In late 2014 and early 2015, eruptions created a small new island and disrupted air travel to the Pacific archipelago.

Earth imaging company Planet Labs PBC had watched the island after a new vent began erupting in late December. Satellite images showed how drastically the volcano had shaped the area, creating a growing island off Tonga.

The UN World Food Program is exploring how to bring in relief supplies and more staff and has received a request to restore communication lines in Tonga, Mr Dujarric said.

One complicating factor is that Tonga has managed to avoid outbreaks of Covid-19. New Zealand said its military staff were vaccinated and willing to follow Tonga’s protocols.

New Zealand’s military said it hoped the airfield in Tonga would be opened on either Wednesday or Thursday. The military said it had considered an airdrop but that was “not the preference of the Tongan authorities”.

Communications with the island nation is limited 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 repairs could take weeks.

Samiuela Fonua, who chairs the board at Tonga Cable Ltd, said the cable appeared to have been severed about 10 to 15 minutes after the eruption.

A second undersea cable that connects the islands within Tonga also appeared to have been severed, Mr Fonua said.

However, a local phone network was working, allowing Tongans to call each other. But he said the lingering ash cloud was continuing to make even satellite phone calls abroad difficult.