A volcano on Tonga's Hunga Ha'apai island erupted again on Friday, sending ash, steam and gas into the air.

Taaniela Kula, head of Tonga Geological Services, said that the eruption, which had a radius of 260 km, was about seven times more powerful than the last eruption on December 20 last year.

A national tsunami warning issued early on Friday advised Tongans to stay away from coastal areas, after swirling abnormal tides drew crowds to the Nuku'alofa waterfront.