A month after the damaged Pacific nation's double catastrophe of an undersea eruption and tsunami, the subsea cable that connects it to the digital world remains cut.

And there's still no time frame for fixing it, says telecommunications company Digicel.

Meanwhile China and Australia are landing high-tech equipment to support aid efforts and their own sovereign interests in a vast ocean where both have ambitions.

"Australia must be first and foremost giving assistance to Tonga. Failing that China will be there in spades," former prime minister Kevin Rudd tweeted days after the disaster.

China says its emergency aid was first to arrive in the devastated kingdom.

However Telstra has worked with Australia's Department of Foreign Affairs and Trade to get communications equipment shipped on RAAF flights alongside other vital aid.

The telco has huge investments in subsea cables, with approximately 450,000km worth of network.

It says its satellite amplifier technology and dishes have been successfully integrated into Digicel's set up and it will soon to complete its Australian-government backed acquisition of the operator, which provides services in Papua New Guinea, Nauru, Samoa, Vanuatu and Fiji in addition to Tonga.

Meanwhile Telstra says it's in regular contact with those on the ground there.

The Philippines branch of China's Huawei Technologies, which is responsible for its operations in Tonga, was quickly able to communicate with its partners there after the January blast by satellite phone.

"In the wake of the recent disastrous volcanic eruption in Tonga, China acted swiftly and provided emergency assistance through multiple channels," says its embassy in Canberra.

Yet for those impacted by the deadly eruption, there's still a long way to go. Even with plenty of willing partners.

"Communications with and within Tonga continue to be significantly impacted as a result of the disaster," according to its high commission.

"Basic mobile connectivity is now re-established, voice calls and now operational on Tongatapu, and limited data services are also available through GPRS and 3G."

Contact with and within Tonga is remains dependent on satellite technology provided by Australia and other partners.

"It's easy to think about the internet as a really abstract thing," says Justin Sherman, fellow at think tank Atlantic Council's Cyber Statecraft Initiative.

"But in reality, the internet depends on physical infrastructure to run: routers in our house or office building, data servers that hold our favourite movies and social media content, submarine cables that carry internet traffic between continents."

Chinese state media insists its companies and drone technologies could help Tonga restore communications, including repairs to the undersea cable.

If so, base station equipment is needed to directly connect with satellites to allow emergency calls.

Once installed, it could then be supported by unmanned aerial vehicles as was the case during the restoration of communications last year when floods cut off millions of people in Henan Province.

Closer to home, the Lowy Institute says Telstra's purchase of PNG-headquartered Digicel Pacific, underwritten by $1.9 billion from the Australian taxpayer, firmly ties its business operations to Australian foreign policy in the region.

Tonga, like other Pacific nations, is dependent on mobile phone connectivity to access the digital world that many of us take for granted for information, interaction, education, banking, health - and fun.

Foreign Minister Marise Payne's somewhat considered observation is that the Digicel acquisition is "fundamentally in the interests of both Australia and our Pacific family".

In January, Australia also signed an agreement with Palau and the Belau Submarine Cable Corporation (BSCC) to finance an undersea fibre optic cable which will connect to a US-Singapore trunk cable.

"Infrastructure projects such as this lie at the heart of our collective vision for a secure, stable, open and prosperous Indo-Pacific" Australian Ambassador to Palau Richelle Turner says.

The project builds on Australia's support for the 4700km of the Coral Sea Cable System cable connecting Sydney, Port Moresby and Honiara, as well as assistance to Timor Leste for its first undersea cable.

It was the first under the Trilateral Infrastructure Partnership Investment in the Indo Pacific.

As such, Telstra should replace all Huawei equipment currently used in Digicel's Pacific networks with technology that does not fall under the Chinese Communist Party's jurisdiction to see any national security pay-off in that deal, according to Lowy experts Mihai Sora and Jonathan Pryke.

Researchers say the volume and sensitivity of information travelling along the vital subsea cables is upping the geopolitical stakes, not just at the choke points in big economies.

Company and government information being sent to the "cloud" is actually travelling under the sea via a network of several hundred submarine cables.

Submarine cables have been around for decades, first carrying telegraph communications under the sea and now up to 97 per cent of intercontinental internet traffic.

Nor would the internet exist without these long tubes running along the ocean floor worldwide, Mr Sherman says

Sometimes they get damaged accidentally when snagged by a fishing vessel or can be disrupted by natural disasters.

"There is also broader concern, though, that a nation-state could deliberately target submarine cables if it so chose to disrupt internet connectivity during conflict.

"Much of our global internet's 'globalness' depends on these hundreds of cables along the ocean floor and if they are damaged, disrupted or degraded in significant ways, those impacts will be felt from government agencies and business offices all the way down to the smartphone in your hands."

Satellite phones have provided a helpful but costly alternative for diplomats and emergency workers in Tonga, but not for most families and small businesses.

The Tonga High Commission says repairing international and domestic communication cables cut by the eruption is a priority.

A preliminary investigation has established there are two undersea cable breaks, one to the domestic wire near the eruption and another to the international link between Tongatapu and the cable landing station in Suva, Fiji.

Australia is working with Tonga on connectivity options, including possibly providing antenna and other communications equipment.

Initial efforts to help Tonga connect to the outside world have allowed the 40,000-plus Tongan community in Australia and elsewhere to connect with family and friends, says the High Commission in Canberra.

"Tonga is a member of the Pacific family and Australia is standing by Tonga in its time of need."

France, New Zealand, the US, Japan, Fiji and the UK were recognised in the statement to mark the one month anniversary of the unprecedented disaster, from which Tonga says it will take years to recover.

At a handover ceremony in Tonga, China was thanked for its delivery of more than 110 bulldozers, trucks and excavators.

"We are fortunate to have among our good friends countries like China to support us," Tonga's Prime Minister Siaosi Sovaleni said.

Foreign Ministry spokesperson Wang Wenbin says China's support to Tonga for emergency disaster relief and post-disaster reconstruction is a testament to their comprehensive strategic partnership.

China intends to continue to work with Pacific Island countries on "a shared future".

There's also talk of billionaire Elon Musk providing Tonga a connection to Starlink - a network of low-orbit satellites for internet services - but SpaceX couldn't confirm any follow though on the ground.

Australian Associated Press