Dramatic video footage was posted to social media; including of some of the first waves to hit the shoreline, of cars narrowly avoiding the flood waters, at least one vehicle being swept away, and of families stuck in church buildings as waves rushed by.
One local wrote on Facebook: "A volcanic explosion just erupted and people have evacuated to higher ground now from possible tsunami waves also ash shards are falling and now the ash clouds are covering the island of Tongatapu.
"We live in Kolomotu'a near the ocean so we have left already and we are in our cars heading out but traffic on every road. Please pray for us as a family and safety."
The US Storm Watch website said the eruption was "one of the most violent volcano eruptions ever captured on satellite".
Civil Defence officials stated: "We expect New Zealand coastal areas on the north and east coast of the North Island and the Chatham Islands to experience strong and unusual currents and unpredictable surges at the shore."
Officials from both Fiji and American Samoa have also issued warnings to their populations over potential tsunami.
New Zealand's MetService also said the eruption had resulted in a "pressure surge" which had been observed in its weather stations across New Zealand tonight.
As well as people in Fiji reporting hearing the eruption, people from Hawke's Bay and Papamoa also claimed to have heard the volcanic event.
Volcanic ash was raining down on the capital city of Nuku'alofa.
When the tsunami warning was announced, police and local authorities advised all residents to move to higher ground.
The loud eruption was heard as far away as Fiji, with Anthony Brown – who is in Nadi – last night telling the Herald: "For the last hour there have been continuous explosive sounds with continuous rumbling, windows rattling and doors rattling."
Footage posted on Twitter shows waves flowing into the streets from a beach in Tonga.
The Hunga Tonga-Hunga Haʻapai volcano is about 30km southeast of Fonuafo'ou island in Tonga. It had been active from December 20, 2021, but was declared dormant on January 11.
On Friday, several Tongan geologists went to observe the Hunga Tonga-Hunga Haʻapai volcano.
Taaniela Kula, Deputy Secretary, Ministry of Lands and Natural Resources – who was in charge of the group – told local media outlet Matangi Tonga: "Yesterday there were massive explosives, thundering lightning within two miles away, we observed and recorded.
"Big day yesterday indeed!. It was great getting out there during the volcano's peak hours. It's a geologist's dream to see actual geological events in process."
The ongoing plumes of debris from the volcano earlier saw a halt of flights in Tonga.
As of Friday, the maximum tsunami wave had been recorded in Nuku'alofa tide gauge at 12.30pm and was about 30cm above sea level.
Prior to yesterday's big eruption, Tongan Government officials urged locals to both be wary of ash in the atmosphere from the eruption and while in the water.
"Sometimes volcanic ash in the atmosphere is not visible but stinging on the eyes or irritation are signs," they said.
"If dark coloured particles are observed on outdoor surfaces at a large scale, it may also be a sign of ashfall. It is advised to stay indoors and to protect your rainwater harvestings. Please ensure to cover your water reservoirs. If one feels short of breath please wear a mask to reduce inhalation of ash from the air.
"Strange oceans and nearshore turbulence were seen in the shores of Ha'apai and Tongatapu islands. These are caused by the volcanic eruption and these dynamic currents can cause chaos if one tries to sail or swim in it. It is advised that the public stay out of the water until further notice."
