Video posted on social media shows large waves washing ashore in coastal areas. The Tonga Meteorological Services says a tsunami warning has been put in force covering all of the island.
New Zealand’s National Emergency Management Agency tweeted: “We have issued a NATIONAL ADVISORY: TSUNAMI ACTIVITY following the Tongan eruption.
“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.”
Reuters reports that tsunami waves measuring two feet in height were observed by sea-level gauges at the capital of the US territory of American Samoa following volcanic activity in Tonga, the U.S.-based Pacific tsunami warning center said.
The tsunami monitor said in a statement that the tsunami threat continues and sea level fluctuations as well as strong ocean currents pose hazards along beaches and harbours.
Video shared on social media by BNO News shows the sky turned pitch black.
BNO News tweeted: “Sky turns pitch black as volcano eruption and tsunami hit Tonga.”
Australia’s 9 News reports satellite footage showing the Hunga-Tonga-Hunga-Ha’apai volcano erupting on Saturday evening local time after sustained volcanic activity in the area since Friday.
Jared Silverman tweeted alongside a clip of the eruption recorded by satellite: “As a meteorologist, I’ve seen many things on satellite. None as frightening as this Tonga volcanic eruption!”
The Matangi Tonga news site reported that scientists observed massive explosions, thunder and lightning near the volcano after it started erupting.
It said satellite images showed a 5km-wide plume of ash, steam and gas rising up into the air to about 20km.
Dr Faka’iloatonga Taumoefolau tweeted that he could hear the eruptions and it sounded “pretty violent”.
He added: “Raining ash and tiny pebbles, darkness blanketing the sky.”
The eruption at 0410 GMT of the Hunga Tonga-Hunga Ha’apai underwater volcano, located about 65 km (40 miles) north of Nuku’alofa, caused a 1.2 metre tsunami, Australia’s Bureau of Meteorology said.
The agency said it continued to monitor the situation but no tsunami threat had been issued to the Australian mainland, islands or territories.
Tsunami waves of 2.7 feet were observed by gauges at the Tongan capital of Nuku’alofa and waves of 2ft at Pago Pago, the capital of American Samoa, the Pacific Tsunami Warning Center said.
Fiji issued a tsunami warning, urging residents to avoid the shorelines “due to strong currents and dangerous waves.”
Jese Tuisinu, a television reporter at Fiji One, posted a video on Twitter showing large waves washing ashore, with people trying to flee from the oncoming waves in their cars.
He said: “It is literally dark in parts of Tonga and people are rushing to safety following the eruption.”
On Friday, the volcano sent ash, steam and gas up to 12 miles (20km) into the air, Tonga Geological Services said in a Facebook post. It has a radius of 160 miles (260km).