A thick blanket of ash from a huge undersea volcanic eruption has covered the Pacific Island nation of Tonga, contaminating water supplies, cutting off communications and preventing surveillance flights assessing the extent of damage from tsunami waves that are believed to have inundated entire towns. 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. There were still no official reports of injuries or deaths by Sunday evening, with communications limited. Families outside Tonga were waiting desperately for news, as communications remained down across most of the country, nearly 48 hours since the huge undersea volcano eruption, which could be heard and felt more than 2,000km away. Tonga’s cabinet held a crisis meeting on Sunday and was asking for assistance, said the office of Zed Seselja, Australia’s minister for the Pacific. A surveillance flight was scheduled to depart Australia for Tonga on Monday morning to assess damage to critical infrastructure such as roads, ports and powerlines and determine the next phase of the response effort. However, the plane was unable to depart, due to the ash cloud blanketing Tonga. A Royal New Zealand Air Force Orion plane managed to depart from Auckland on Monday to assess initial damage in the area. Aid agencies said thick ash and smoke had prompted authorities to ask people to wear masks and drink bottled water. In a video posted on Facebook, Nightingale Filihia said she was sheltering at her family’s home as volcanic ash and tiny pieces of rock rained down and turned the sky pitch black. “It’s really bad. They told us to stay indoors and cover our doors and windows because it’s dangerous,” she said. “I felt sorry for the people. Everyone just froze when the explosion happened. We rushed home.” Outside the house, people were seen carrying umbrellas for protection. Jacinda Ardern, the prime minister of New Zealand, told a news conference on Sunday that contact had not been established with coastal areas beyond the capital, Nuku‘alofa. “Nuku‘alofa is covered in thick plumes of volcanic dust but otherwise conditions are calm and stable,” Ardern said. “We have not yet received news from other coastal areas.” She said the main undersea communications cable was affected, probably due to loss of power. She added that power was being restored in some areas on the islands and local mobile phones were slowly starting to work. The New Zealand high commission in Nuku’alofa said the tsunami had damaged boats, shops and other infrastructure. The International Federation of the Red Cross expressed concerns about Tonga being “cut off from the rest of the world”. “From what little updates we have, the scale of the devastation could be immense, especially for outer lying islands,” said Katie Greenwood, IFRC’s Pacific Head of Delegation. The IFRC was particularly concerned about access to safe and clean drinking water as a result of saltwater inundation caused by the tsunami waves and ash fall from the volcanic eruption, as well as shelter for communities, particularly on the coastline. Dave Snider, the tsunami warning coordinator for the National Tsunami Warning Center in Palmer, Alaska, said it was very unusual for a volcanic eruption to affect an entire ocean basin, and the spectacle was both “humbling and scary”. The tsunami waves caused damage to boats as far away as New Zealand and Santa Cruz, California, but did not appear to cause any widespread damage. Snider said he anticipated the tsunami situation in the US and elsewhere to continue improving. Tsunami advisories were issued earlier for Japan, Hawaii, Alaska and the US Pacific coast. The US Geological Survey estimated the eruption caused the equivalent of a magnitude 5.8 earthquake. Scientists said tsunamis generated by volcanoes rather than earthquakes were relatively rare. As the tsunami struck on Saturday, a video shot from the roof of a building on the coast showed large waves breaching the coastal wall seconds apart, while a video shot from the New Zealand high commission in Nuku’alofa, where people ran for shelter, showed the downtown area of Patangata had been completely submerged, including the Royal Palace and Tonga’s largest bank. Another video, shot inside a church, showed children crying out as water surrounded the building and waves began lapping against the windows. In a video posted to YouTube after the eruption, Abraham Leilua begins by telling his followers that “it’s not that bad” but within minutes, as the water rises, he says “I have to run for my life” before ending the video. Blake Smith-Tatafi, a Tongan based in Australia, said they were praying and in fear. “If you don’t know, the island of Tonga is flat. This leaves their people with nowhere of realistic safety to evacuate. Villages completely underwater. We haven’t had contact for hours now. This is a crisis.” Pita Taufatofua, a Tongan Olympian based in Australia, said he had not heard from his father or family in Ha‘apai, the lowest-lying islands in Tonga. “Initial reports of damage have been catastrophic and all communications with Tonga have been wiped out,” he said. “Whilst I can’t assist family at this moment I will focus on country as more information comes out.” Southern Cross Cable Network said on Sunday it had been able to confirm contact with a communications centre in Tonga and work was under way to have internet and phone links restored. A tweet on Sunday morning stated that the Tongan prime minister, Siaosi Sovaleni, said the tsunami warning remained in place and much of the country had sustained serious damage. Australia’s foreign affairs department said its high commission had received no reports of casualties. However, there were reports that a UK woman Angela Glover, who ran a tattoo parlour in Nuku’alofa, was missing after being swept away in the tsunami. Social media posts from her family and friends said she had not been heard from since the disaster and they were appealing for news of her. Ardern said the situation in Tonga was “hugely concerning”. “Communication, as a result of the eruption, has been difficult, but our defence force team and Ministry of Foreign Affairs are working as we speak to establish what’s needed and how we can help,” she said. New Zealand has made an initial NZ$500,000 (£249,000) available to Tonga and has dispatched an aerial surveillance aircraft to assess the damage. Ardern said she had been in touch with Scott Morrison, the Australian prime minister, and that both governments stood ready to respond to Tonga’s needs. But conditions were not immediately safe for aircraft. “There’s an urgency here. We want to make sure we’re on the ground as soon as possible, but for our navy vessels it will take several days to reach Tonga, and we need to finely balance the need to get there quickly but to make sure we also get the people and resources they need there as well, and in some cases we have parts of Tonga where we just haven’t been able to establish communication.” The US secretary of state, Antony Blinken, said he was “deeply concerned” about the people of Tonga and that the US stood prepared to provide support. Shairani Ali, the chief executive of Save the Children Fiji, said the charity was closely monitoring the situation and prepared to respond. “Our thoughts have been for the safety of our Tongan brothers and sisters, and Save the Children is well placed to assist as needed,” she said, adding that the “booms from the eruption of the Tonga volcano could be clearly heard in Fiji”. The volcano, Hunga Tonga-Hunga Ha‘apai, at 1,800 metres high and 20km (12.5 miles) wide, is 65km (40 miles) north of Nuku‘alofa. US Storm Watch said the eruption was one of the most violent ever captured on satellite, while Tonga’s geological service said the gas, smoke and ash from the eruption reached 20km into the sky. The eruption could be heard 2,300km (1,400km) away in New Zealand, while tsunami warnings were in force at various times across the Pacific, including in Australia, Japan and the US. Some coastal communities in Fiji and Vanuatu were damaged by large waves, while tidal surges were reported to have damaged harbours and coastal parks along the US west coast. Satellite imagery appeared to show Tonga’s uninhabited Nuku and Tau islands completely eroded. Tonga has also been hit by two category five cyclones in the last five years: Cyclone Harold in April 2020 and Cyclone Gita in 2018. In Japan, about 230,000 people were advised to evacuate across eight prefectures as waves of more than a metre hit coastal areas, the public broadcaster NHK reported. The alert included areas hit by the deadly 2011 tsunami.