Tsunami waves have hit the Kingdom of Tonga after a massive volcano eruption, which has sent residents fleeing to higher ground.
Hunga-Tonga-Hunga-Ha'apai has erupted several times over the past week, including Friday, but the latest on Saturday afternoon (local time) sent ash up to about 15,800 metres altitude, according to South Pacific journalist Michael Field, citing the Volcanic Ash Advisory Center Wellington.
Images show a huge plume of ash covering Tonga's main island and fast-moving waves making landfall.
Tonga Meteorological Services shared maps showing the spread of the ash over the islands.
"This is an image of the eruption, it covers the whole of the Ha'apai, Tongatapu and Eua island groups," the agency said.
Tongatapu is a mostly flat island, with its highest point only 28m above sea level.
The eruption accorded just before 5.30pm local time (3.30pm AEDT), with the United State Geological Service (USGS) also registering a 4.0 earthquake at the same time.
The Islands Business news site reported a convoy of police and military troops evacuated Tonga's King Tupou VI from his palace near the shore. He was among the many residents headed for higher ground.
Huge traffic jam as residents try to flee
One local told Yahoo News the eruption was "catastrophic", and there was ash and volcanic rock raining down on the country’s capital, Nuku'alofa.
Another said she was stuck in traffic attempting to flee to higher ground, and within an hour the sky had become as black as night.
According to multiple residents, no tsunami sirens were activated.
A Twitter user identified as Dr Faka'iloatonga Taumoefolau posted video showing waves crashing ashore.
"Can literally hear the volcano eruption, sounds pretty violent," he wrote, adding in a later post: "Raining ash and tiny pebbles, darkness blanketing the sky."
Earlier, the Matangi Tonga news site reported that scientists observed massive explosions, thunder and lightning near the volcano after it started erupting early on Friday.
Satellite captures 'violent' eruption: 'Like Hiroshima'
According to US Storm Watch, the eruption was one of the "most violent" ever captured on satellite footage.
"Looks like Hiroshima," one person commented.
Residents more than 700km in Fiji and 600km away in Niue reported hearing the eruption.
A tsunami warning was in place for American Samoa following Hunga Tonga's eruption, but has since passed.
The Joint Australian Tsunami Warning Centre said a 1.2m tsunami wave was observed at Nuku'alofa in Tonga at 3.30pm AEDT.
There was no tsunami threat to Australia.
The National Emergency Management Agency said some parts of New Zealand could expect "strong and unusual currents and unpredictable surges at the shore following a large volcanic eruption".
Hunga Tonga was formed after an undersea eruption in December 2014.
The volcano was erupting intermittently in late December, but Friday's eruption was about seven times more powerful than the last eruption and continuing to grow, Tonga Geological Services (TGS) said. The strength of Saturday's eruption is unclear.
The volcano is located about 2000km northeast of New Zealand.
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