Another tsunami warning issued for Tonga

Tonga has been struck by a tsunami on Saturday after the Hunga-Tonga-Hunga-Ha'apai underwater volcano erupted.

Tonga's Meteorological Services says a warning is in place for the entire island, and the population is racing to evacuate in complete darkness as a wall of water surges inland.

Warning sirens have gone off across Nukualofa as authorities urge the public to move to safety.

"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," a local wrote.

"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."

A chilling video filmed from a roof shows a massive surge of water inundating the land as it pours in. Early reports say the tsunami was 1.5 metres tall.

People are rushing to evacuate in complete darkness. Images show traffic crawling to safety with their headlines on.

"Raining ash and tiny pebbles, darkness blanketing the sky," Dr Faka'iloatonga Taumoefolau posted to Twitter.

Fiji One reporter Jese Tuisinu posted to Twitter describing it as "literally dark" and said people were "rushing to safety".

One video shows vehicles racing ahead of the sea as it chases in.

But not everyone could escape the tsunami in time. Footage shows young children trapped in what appears to be a small church close to the sea as water smashes against the windows.

The eruption has been described as "one of the most violent volcano eruptions ever captured on satellite", with footage showing a massive ring of ash exploding upwards.

A tsunami advisory has been issued for American Samoa, while there are reports in Fiji of large waves striking the islands.