It could be weeks before Tonga’s crucial undersea cable – which connects it to the world – is back online.

The cable carries nearly all digital information including the internet and phone communications in and out of Tonga.

It was damaged after the Hunga Tonga-Hunga Ha’apai volcanic eruption nearby on Saturday.

Dean Veverka is the director of the International Cable Protection Committee and chief technical officer for Southern Cross Cables – which owns two other cables in the area.

The Tongan cable, which is part-owned by the Tongan government, has broken about 37km off Tonga, he said.

The repair requires a ship which is currently in Papua New Guinea about 2500 kilometres away, so it could be a couple of weeks before the cable is back up and running.

“It’s very serious because the satellites can only handle … a small percentage of the traffic requirements out of any country.

“These days’ submarine cables carry about 99 percent of all communications between countries.

“It will be quite limiting the communication to Tonga for a fair while.”

It could cost anywhere from $US250,000 upwards to repair, he said.

In the meantime, satellite communications appear to be disrupted by the massive ash cloud thrown up by the volcano.

NZ Joint Forces commander rear admiral Jim Gilmour told RNZ on Monday the communication problems – likely from the ash – prevented pictures taken during the reconnaissance flight being sent back to New Zealand for analysis from the air.

It had to be done once the plane landed back in New Zealand on Monday evening.

The Tonga cable connects into Suva in Fiji, and from there to the Southern Cross cable onto New Zealand, Australia and the U.S.