Tsunami-hit 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 , triggering 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.
Tsunami warnings were also issued for parts of Australia's east coast, and remained in place for New South Wales, and Lord Howe and Norfolk islands as of 12:30 AEDT on Sunday.
Internet and phone lines went down at about 6.40pm local time on Saturday, leaving the 105,000 residents on the islands virtually uncontactable.
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 2,383 kilometres northeast of New Zealand.
"Nuku'alofa is covered in thick plumes of volcanic dust but otherwise conditions are calm and stable," Ms Ardern said.
"We have not yet received news from other coastal areas."
New Zealand Prime Minister Jacinda Ardern. Source: SBS / , APEC New Zealand
Satellite images captured the volcanic eruption on Saturday as the explosion sent plumes of smoke into the air and about 19 kilometres (12 miles) above the sea level. The sky over Tonga was darkened by the ash.
Concerns were growing among the Tongan community in New Zealand, desperate to make contact with their families back home. Some churches organised community prayers in Auckland and other cities.
"We pray God will help our country at this sad moment. We hope everybody is safe," Maikeli Atiola, the Secretary of the Wesleyan Church of Tonga in Auckland said, Radio New Zealand reported.
Ms Ardern said the main undersea communications cable has been impacted, likely due to loss of power.
Power was being restored in some areas on the islands and local mobile phones were slowly starting to work, she added.
Official damage assessments were not yet available, she said. But Ms Ardern said the New Zealand high commission in Nuku'alofa had said the tsunami has damaged boats, shops and other infrastructure.
An Australian government spokesperson said initial assessments are still underway but Australia is ready to provide support to Tonga if requested.
The Hunga-Tonga-Hunga-Ha'apai volcano has erupted regularly over the past few decades but Saturday's eruption was so loud that residents 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 750 kilometres 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.
The eruptions triggered tsunami warnings across the Pacific, with the United States urging people on its Pacific coastline to stay away from the shores and Australia's NSW and Queensland regions closing beaches.
Hundreds of thousands of Japanese citizens were advised to evacuate as waves of more than a metre hit coastal areas.