Tonga Volcanic Eruption, Tsunami Causes Significant Damage

There have been no official reports from Tonga of casualties or deaths. Videos posted online not long after the eruption and information relayed by New Zealand diplomats on Tonga’s largest island, Tongatapu, indicated significant damage to property.

The situation on other Tongan islands remains uncertain due to a paucity of information that partly stems from power blackouts and loss of communications. The submarine cable that provides much of Tonga’s international connectivity is likely not operating because of power loss, according to New Zealand’s government, rather than being damaged.

Calls to government offices, emergency services and hotels in the Tongan capital Nuku’alofa didn’t connect on Sunday. Kentik, an internet monitoring service, said connectivity with Tonga plummeted to zero early Saturday evening in the aftermath of the eruption.

Filipo Motulalo, a resident of New Zealand’s largest city Auckland, said it was an intensely worrying time for Tonga’s diaspora communities. He had been unable to contact family in Tonga since Saturday evening. Initially people had been able to make contact over social media, but that too had shut down, he said.

“People are feeling anxiety,” said Rev. Kalolo Fihaki, superintendent of the Tongan Synod of the Methodist Church of New Zealand. Tongans in Australia and New Zealand on Sunday created a prayer chain using Zoom with about 3,000 people participating, he said. According to Rev. Fihaki, clean water is likely to be the most pressing need for low-lying Tonga.

New Zealand Prime Minister

Jacinda Ardern

said on Sunday that the government has been able to communicate with its diplomats in the capital by satellite phone. They and New Zealand’s military are working to ascertain what assistance is needed for Tonga, a nation of about 100,000 people.

“The tsunami has had a significant impact on the foreshore of the northern side of Nuku’alofa with boats and large boulders washed ashore. Shops along the coast have been damaged and a significant clean up will be needed,” Ms. Ardern said.

The capital Nuku’alofa is covered in a thick film of volcanic dust, but is otherwise calm and stable, she said. “However I would note we have not yet received information from other coastal areas of Tongatapu or the outer islands,” she added.

Tonga has agreed to New Zealand sending an air force surveillance plane to assess damage to the archipelago once the towering ash cloud from the eruption has dissipated enough to make that safe to do. New Zealand’s navy is also getting prepared to send a frigate or other vessel, depending on the specific requirements of the relief effort.

An initial aid pledge of 500,000 New Zealand dollars—equivalent to about $340,000—is just the beginning of the country’s assistance to Tonga, Ms. Ardern said. An Australian government spokeswoman said it stands ready to provide support to Tonga if requested.

Video posted online by a Tongan government worker who identified himself on Twitter as Faka’iloatonga Taumoefolau showed fast moving but relatively low waves crashing ashore and inundating homes. Other posts from Mr. Taumoefolau described the sound of the eruption as “pretty violent” and reported significant ash fall and darkened skies.

Tonga’s consulate to the European Union posted images of flooded coastal areas and properties on its Twitter account and said damage was extreme. U.N. Secretary-General

António Guterres

said he was following the situation with concern and U.N. offices in the Pacific are on standby to provide support if needed.

Wave surges and tsunami waves were experienced as far afield as New Zealand and Japan, while the Australian state of New South Wales closed beaches as a precautionary measure.

New Zealand media published photos of boats damaged by wave surges in a marina in the far north of the country.

Tsunami waves as tall as 1.2 meters (3.9 feet) were recorded in one remote Japanese region early Sunday morning and as high as 1.1 meter in a part of northern Japan, according to the Japan Meteorological Agency. No injuries were reported.

Video footage showed some ships docked on the island of Shikoku sank after the tsunami wave arrived in the middle of the night. In some regions including places that were struck by tsunamis after Japan’s March 2011 earthquake, sirens roused people in the middle of the night to evacuate their homes.

The Tongan volcano, Hunga Tonga-Hunga Ha’apai, has had a series of eruptions in recent weeks and has formed a new small island in the Pacific.

Tonga, in the southwestern Pacific Ocean, is an archipelago of about 170 islands formed by ancient volcanic eruptions. Once part of the British Empire, Tonga regained full independence in 1970. Its economy is reliant on agriculture and trade with New Zealand and Australia.

—Peter Landers in Tokyo and James Glynn in Sydney contributed to this article.

Write to Stephen Wright at stephen.wright@wsj.com