Local journalist Mary Fonua told New Zealand’s 1News the country had had “a very frightening hour” following a series of “huge explosions” at the volcanic island 65 kilometres away.
Ms Fonua described seeing “this long white wave… coming from the horizon.
“After about three waves it had come over the road and into our garden, and our car was washing against the front post.
“The waves have continued to come in,” she said.
She was concerned that the waves were heading towards a low-lying settlement housing “thousands of people” on a narrow peninsula.
But she said warnings in recent days, including from police with loudspeakers, had kept people out of the water.
Tsunami expert Andrew Gissing, general manager of Risk Frontiers, said while the volcano’s recent activity had resulted in a marine tsunami warning on Friday, the eruption on Saturday “seems much bigger” and it appeared the waves had hit the central business district.
“There are hotels, lots of shops nearby and eateries right by the water,” he said. “So there are certainly concerns. The key thing is the volcano is active, and there could be further eruptions.”
A spokesperson for the Australian government said Tonga “is part of our Pacific family and our thoughts are with the entire community dealing with the impact of the volcanic eruption and tsunami.
“The Prime Minister and Minister for Foreign Affairs are monitoring the situation and Australia stands ready to provide support to Tonga if requested. Initial assessments are still underway and DFAT is working to ensure Australians in Tonga are safe and accounted for.”
The scale of the under-sea eruption has been captured in dramatic satellite imagery, while surges in atmospheric pressure have been detected in Australia and New Zealand likely caused by the gravity wave generated by the explosion.
Fiji residents also reported being able to hear and feel the eruption, as the country issued an advisory warning those in low-lying areas to stay out of the water and away from the shore. Hours later Vanuatu also issued an alert, and there are reports of some inundation in Port Vila.
New Zealand issued a tsunami advisory to coastal areas on the north and east coast of the North Island and Chatham Islands, warning of “strong and unusual currents and unpredictable surges at the shore”.
A spokeswoman for the Australian Bureau of Meteorology said “we are keeping a really close eye on the observations across the South Pacific” to see what happens with the waves that have been produced so far, and any further volcanic activity.
It comes after the same volcano erupted on Friday, sending ash, steam and gas 20 kilometres into the air, Radio New Zealand reported.
The volcano is located about 30 kilometres south-east of Fonuafo’ou island in Tonga. It was erupting intermittently in late December.
Radio New Zealand earlier reported that Tonga Geological Services head Taaniela Kula said the eruption had a radius of 260km.
It was about seven times more powerful than the last eruption on December 20 last year and continuing to grow, Kula earlier told RNZ.