Three days after the massive eruption of the submarine volcano Hunga-Tonga-Hunga-Ha'apai in the Pacific, the extent of the damage and the number of possible victims are still unclear.

The United Nations Office for the Coordination of Humanitarian Affairs (OCHA) said there was no contact specifically with the Ha'apai archipelago.

After the tsunami triggered by the volcano, there is particular concern about the low-lying islands of Mango and Fonoi.

A distress signal was received from Mango.

"Communication continues to be the biggest problem as the internet and international phone lines are still down," the UN agency said. Satellite phones are the only reliable means of communicating with the outside world, but they don't always work reliably either. "Overall, there seems to be significant damage to the infrastructure around the main island of Tongatapu." Many islands are said to be covered by a layer of ash. As satellite images show, the ash cloud is now drifting towards the east coast of Australia.

New Zealand wanted to send two ships with relief supplies to Tonga on Tuesday.

A formal request for assistance from Tonga is still pending, but the New Zealand government wants to dispatch the ships HMNZS Wellington and HMNZS Aotearoa as they took three days to reach the affected region, it said.

"The communication problems caused by the outbreak make this disaster relief particularly challenging," said New Zealand Foreign Minister Nanaia Mahuta.

Desalination plant on board

One of the ships is primarily intended to transport urgently needed drinking water.

"Water is a top priority for Tonga at this stage and HMNZS Aotearoa can transport 250,000 liters and produce 70,000 liters per day through a desalination plant," Defense Minister Peeni Henare said.

On Saturday, the Hunga-Tonga-Hunga-Ha'apai threw a gigantic cloud of ash kilometers high and triggered tsunami waves that even swept onto the coasts of Japan, Alaska and South America.

The volcano is just 40 miles from Tonga's capital, Nuku'alofa.

The Feuerberg lying under the water surface is 1800 meters high and 20 kilometers wide.

The archipelago of Tonga has around 107,000 inhabitants.