Relief agencies began sending aid to Tonga on Monday (January 13) as low-lying islands in the South Pacific archipelago were battered by a strong cyclone at the weekend.

Early reports from emergency workers said that category five Cyclone Ian and its associated hurricane-force winds had caused significant damage to islands in the north.

TV 3 New Zealand reported that as damage assessments continue the government is concerned about the number of people without homes.

"Presumably it will be in the thousands, so hopefully what we are able do today is just to ease some of the pressures on the people," said government spokesperson, Lord Tuivakano.

The local hospital has difficulty treating injured people as most of the emergency medical supplies have been damaged and there is no power or running water.

There were communication problems with 80 percent of the worst-hit Ha'apai island group, including Lifuka, which bore the brunt of the storm but mobile phone reception is slowly being restored.

About 8,000 people live in the Ha'apai islands, which are about 1,630 miles northeast of the New Zealand capital, Wellington.

Two Tongan navy patrol boats were on their way to the Ha'apai Islands group with emergency shelter supplies and road clearing equipment. The Red Cross has sent a chartered flight with health, power and telecommunications experts.

The United Nations' Office for the Coordination of Humanitarian Affairs said a mapping specialist was due to arrive in the islands on Monday to assess its response.

Presented by Adam Justice