WELLINGTON (AFP, REUTERS, XINHUA) - Tonga’s capital Nuku’alofa suffered “significant” damage in the powerful volcanic eruption which triggered a tsunami but there had been no reports of injury or death, New Zealand Prime Minister Jacinda Ardern said Sunday (Jan 16).

“The tsunami has had a significant impact on the foreshore on the northern side of Nuku’alofa with boats and large boulders washed ashore,” Ardern said, adding her government had made contact with the New Zealand embassy in the Tongan capital after communications with the island were cut following the eruption.

She also pledged to provide support for Tonga and made an initial sum of NZ$500,000 (S$457,290) available to the Pacific island.

Tonga remained largely uncontactable on Sunday with telephone and internet links severed, leaving relatives in faraway New Zealand praying for their families on the Pacific islands as casualty reports had yet to come through.

An underwater volcano off Tonga erupted on Saturday, triggering tsunami warnings of 1.2-metre tsunami waves and evacuation orders on the shores of Tonga as well as several South Pacific islands, where footage on social media showed waves crashing into coastal homes.

Internet and phone lines went down at about 6.40pm local time (1.40pm Singapore time) on Saturday, leaving the 105,000 residents on the islands virtually uncontactable.

"The images of the volcanic eruption in close proximity to Tonga are hugely concerning," Ms Jacinda Ardern, the Prime Minister of New Zealand, which is located about 2,383km from Tonga, said in a statement on Instagram.

"Communication as a result of the eruption has been difficult, but our defence force team and Ministry of Foreign Affairs are working as we speak to establish what's needed and how we can help," she said.

There are no official reports of injuries or deaths in Tonga as yet although communications are limited and contact has not been established with coastal areas beyond the capital Nuku’alofa, Jacinda Ardern the Prime Minister of New Zealand told a news conference on Sunday.

Tonga, an island nation with around 105,000 residents, lies 2,383km northeast of New Zealand.

In Japan, hundreds of thousands of people were advised to evacuate on Sunday as waves of more than a metre hit coastal areas, public broadcaster NHK reported.

Around 230,000 people were advised to evacuate across eight prefectures due to the tsunami risk, NHK reported. The alert included areas hit by the deadly 2011 tsunami.

Ten boats were capsized in Kochi prefecture on Shikoku island in southern Japan, NHK said, and Japan Airlines cancelled 27 flights at airports across the country.

UN Secretary-General Antonio Guterres on Saturday expressed his deep concern over the disaster.

“The United Nations offices in the Pacific are closely monitoring the situation and are on standby to provide support if requested. The secretary-general is grateful to countries that have already offered their support,” Farhan Haq, deputy spokesman for the secretary-general, said in a statement.

The International Federation of Red Cross and Red Crescent Societies Pacific Office in Suva, Fiji, said it was monitoring the situation and had no updates on damages or casualties.

Tongan churches in New Zealand organised prayers for their families back home.

"We pray God will help our country at this sad moment. We hope everybody is safe...," secretary Maikeli Atiola of the Wesleyan Church of Tonga in Auckland said, Radio New Zealand reported.

Pacific impact

The Hunga-Tonga-Hunga-Ha'apai volcano has erupted regularly over the past few decades but Saturday's eruption was so loud that residents in parts of faraway Fiji and New Zealand said they heard it.

“My entire house was shaking,” said Sanya Ruggiero, a Consulting Communications Advisor based in Suva, the capital of Fiji, some 750km from Tonga.

“My doors, windows were all rattling like hell. And mine was not even as bad as others. Hundreds of people ran out of their homes,” said Ruggiero, who consults for several agencies including the United Nations.

Rumblings and eruptions from the volcano continued to be heard through the night, Ruggiero said. Hundreds of people were moved to evacuation centres in Suva.

Fiji Airways had to cancel all its flights due to the ash clouds.

“This is the worst disaster Tonga has had in living memory and the recovery from this is going to take years,” Ruggiero said.

Experts said the ash fallout could contaminate drinking water and cause respiratory issues.

“Help will be needed to restore drinking water supplies.

People of Tonga must also remain vigilant for further eruptions and especially tsunami with short notice and should avoid low lying areas,” said Shane Cronin, professor at the School of Environment, University of Auckland.

Satellite images captured the volcanic eruption on Saturday as the explosion sent plumes of smoke into the air and about 19km above the sea level.

The sky over Tonga was darkened by the ash.

Tonga’s cabinet held a crisis meeting on Sunday and was contacting development partners, a spokeswoman for Zed Seselja, Australia’s minister for international development and the Pacific told Reuters.

She said Australia would sent a P8 surveillance aircraft to Tonga on Monday.

The eruptions triggered tsunami warnings across the Pacific, with the United States and Japan urging people on their Pacific coastlines to stay away from the shores.

US Secretary of State Antony Blinken said on Saturday that the United States is “deeply concerned” for the people of Tonga and pledged support for the island nation.

“Deeply concerned for the people of Tonga as they recover from the aftermath of a volcanic eruption and tsunami. The United States stands prepared to provide support to our Pacific neighbors,” Blinken said on Twitter.

Australia issued a marine tsunami warning for the New South Wales coastlines, Lord Howe Island and Norfolk Island, and said local beaches along the state's coast have been closed. A tsunami advisory was also issued in New Zealand.

The Ecuadorian Navy Oceanographic Institute also on Saturday issued a tsunami warning for Puerto Ayora, the largest town in central Galapagos Islands, some 1,000km west from continental Ecuador.

The agency said in a statement that "significant variations in sea level have been recorded in Academy Bay on Santa Cruz Island", where Puerto Ayora is located.

The tide gauges located on Santa Cruz and Baltra Islands registered "disturbances in the sea level generated by the volcanic eruption", which began to arrive at the shores of the Galapagos Islands at 11.43am on Saturday local time (1.43am on Sunday Singapore time), it said.The agency said that the status of tsunami observation is ongoing for the rest of the Galapagos Islands as well as for the continental coast of the country, adding "other points of the continental and insular coast could experience similar disturbances".