Pacific nations and aid agencies begin coordinating relief efforts in Tonga after a tsunami triggered by a massive volcanic eruption rocked the tiny island nation, causing significant damage.

Satellite images show  the undersea eruption with ash, steam and gas rising above south Pacific waters.
Satellite images show the undersea eruption with ash, steam and gas rising above south Pacific waters. (AP)

New Zealand's military has been able to send a surveillance flight to Tonga to assess the extent of the damage from a huge undersea volcanic eruption while Australia said initial reports suggested no mass casualties in the Pacific island nation from tsunami. 

A New Zealand Air Force P-3K Orion aircraft left from Auckland on Monday to assist in an initial impact assessment of the area and low-lying islands, the New Zealand defence forces said on Twitter.

Red Cross said it was mobilising its regional network to respond to what it called the worst volcanic eruptions the Pacific has experienced in decades.

Australian authorities said their initial reports suggested no mass casualties in Tonga, but added there was "significant damage" to roads and bridges in the country.

"At this stage, fortunately, we have no reports of any mass casualties, which is obviously very good news. But there is still very limited, if any, information coming from the outer islands," Zed Seselja, Minister for the Pacific, told broadcaster ABC.

Australia will send a surveillance flight on Monday to assess the damage, as Pacific nations and aid agencies began coordinating relief efforts.

Significant damage to boats and shops

New Zealand Prime Minister Jacinda Ardern said on Sunday there had not yet been any official reports of injuries or deaths in Tonga, but cautioned that authorities hadn't yet made contact with some coastal areas and smaller islands.

"Communication with Tonga remains very limited. And I know that is causing a huge amount of anxiety for the Tongan community here," Ardern said.

She said there had been significant damage to boats and shops along the Tongan coastline. The capital, Nuku'alofa, was covered in a thick film of volcanic dust, Ardern said, contaminating water supplies and making fresh water a vital need.

Ardern said New Zealand was unable to send a surveillance flight over Tonga because the ash cloud was 63,000 feet high but they hoped to try again on Monday, followed by supply planes and navy ships.

One complicating factor to any international aid effort is that Tonga has so far managed to avoid any outbreaks of Covid-19. 

Ardern said New Zealand's military staff were all fully vaccinated and willing to follow any protocols established by Tonga.

READ MORE: Tonga issues tsunami warning after massive undersea volcano eruption

Tonga begins cleaning efforts 

A towering ash cloud had prevented the military from launching any flights earlier to the Pacific island nation.

People on Tonga described their country as looking like a moonscape as they began on Monday the task of cleaning up from the tsunami waves and ash fall caused by the eruption. 

Communications with the island nation remained limited after the internet was cut soon after the eruption on Saturday evening.

There were no reports of injuries or deaths, although concerns remained for the fate of people on some of the smaller islands near the volcano.

Global cooling

Meanwhile, scientists said they didn't think the eruption would have a significant impact on the Earth's climate.

Huge volcanic eruptions can sometimes cause global cooling as sulfur dioxide is pumped into the stratosphere. But in the case of the Tonga eruption, initial satellite measurements indicated the amount of sulfur dioxide released would only have a tiny effect of perhaps 0.01 Celsius (0.02 Fahrenheit) global average cooling, said Alan Robock, a professor at Rutgers University.

Satellite images showed the spectacular undersea eruption on Saturday evening, with a plume of ash, steam and gas rising like a giant mushroom above the South Pacific waters.

A sonic boom could be heard as far away as Alaska and sent pressure shockwaves around the planet twice, altering atmospheric pressure that may have briefly helped clear out the fog in Seattle, according to the National Weather Service. 

Large waves were detected as far as the Caribbean due to pressure changes generated by the eruption.

In Tonga it sent tsunami waves crashing across the shore and people rushing to higher ground.

With internet and phone lines down, friends and family members around the world were left anxiously trying to get in touch.

Government websites and other official sources remained without updates on Sunday afternoon.

READ MORE: Tsunami threat over after huge Pacific volcanic eruption

'Everyone just froze'

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 was sheltering at her family's home from a rain of volcanic ash and tiny pieces of rock that 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.

Source: TRTWorld and agencies