UNITED NATIONS - The United Nations and its agencies are readying relief efforts for the remote South Pacific island nation of Tonga following the eruption of the Hunga Tonga-Hunga Ha'apai volcano, a UN spokesman said on Monday.

"Our humanitarian colleagues and the government report significant infrastructural damage around Tongatapu (the main island) and no contact from the Ha'apai group of islands," said Stephane Dujarric, the chief spokesman for UN Secretary-General Antonio Guterres. "We are particularly concerned about two small islands, Mango and Fonoi, following surveillance flights confirming substantial property damage."

Australia and New Zealand carried out the flights over the weekend.

While there were no immediate reports of deaths or injuries following Saturday's massive eruption, two people were reported missing, Dujarric said.

He said the World Food Programme is mapping efforts to deploy relief supplies and staff. The agency is sending its emergency communications cluster to help restore communications lines in Tonga.

The spokesman said the UN Children's Fund awaits government confirmation before transporting prepositioned emergency supplies from Fiji and Brisbane, Australia, warehouses. Included are essential water, sanitation and hygiene kits, water containers and buckets and water-field test kits, tarps, recreational kits for children and tents.

The UN Office for the Coordination of Humanitarian Affairs (OCHA) said the tsunami that occurred in the aftermath of the massive eruption has brought extensive damage on the western beaches of Tongatapu, with several resorts and houses destroyed or badly damaged.

Other UN agencies working on relief include the UN Population Fund, the Food and Agriculture Organization, the International Organization for Migration and the World Health Organization, the office said. The agencies work closely with relevant authorities in Tonga, humanitarian partners and donor countries.

The New Zealand and Australian governments announced emergency funding for the immediate aid response, and Australia is preparing a vessel to sail to Tonga with relief supplies, OCHA said.

The Red Cross offered assistance and the Secretariat of the Pacific Community is providing technical support on the impact of the eruption and ashfall, the office said. The Secretariat of the Pacific Community is an international development organization comprising 22 Pacific island countries and territories.

Tonga's National Emergency Management Office is leading assessments and government response. The Tonga Red Cross Society and OCHA provide communication support.

The humanitarian office said there was no serious impact on Fiji, Samoa, Vanuatu and the Solomon Islands besides limited flooding.