New Zealand and Australia have sent planes to assess the damage from a huge undersea volcanic eruption and tsunami that hit the Pacific nation of Tonga on Saturday.

The eruption sent a thick blanket of ash into the sky, contaminating water supplies, cutting off communications and initially preventing surveillance flights assessing the extent of damage.

But on Monday, flights from New Zealand and Australia were finally able to depart.

Videos shared on social media after Saturday night’s eruption showed people running for higher ground as the metre-high floods hit coastal areas and made their way inland while the sky darkened with ash. A sonic boom could be heard as far away as Alaska.