Tsunami-hit Tonga has begun its first COVID lockdown after two cases emerged among wharf workers.

However, officials are confident the infections have not come from aid shipments.

Australian defence personnel, largely from HMAS Adelaide, have so far delivered 168 tonnes of supplies to the Pacific nation that was devastated by a volcanic eruption and tsunami.

Of the 630 personnel on board the ship, there are 23 with the virus and 43 are isolating.

Since the ship left Australia there have been 51 cases detected on the ship, which has a PCR testing facility.

Chief of Joint Operations Lieutenant General Greg Bilton said the two Tongan wharf workers who tested positive were working at a wharf that was not used by HMAS Adelaide.

As well the ship was using a “contactless” process to deliver its supplies.

“I don’t think there was any connection,” he told Sky News on Wednesday.

He said it had been agreed medical samples from the two workers would be taken back to Australia for further testing.

“It doesn’t appear to have evolved from the Adelaide,” he said.

There have been fears an influx of international ships and planes delivering much-needed water, shelter and food after a devastating volcanic eruption had increased the risk of a pandemic outbreak in Tonga.

The country had recorded only one previous COVID case.

Tongan radio station BroadcomFM reported on Wednesday another three cases had been detected in a family, bringing total case numbers to five.

Tongans queued at shops and banks ahead of a lockdown beginning at 6pm, as authorities attempt to stop the spread of COVID.

Health authorities were administering booster shots to the public on Wednesday, with more vaccine booster doses to arrive from Australia and New Zealand.

About 83 per cent of the eligible population have received two doses of vaccine.

In addition to HMAS Adelaide, three New Zealand and one British naval ships, and two Chinese fishing ships from Fiji have come into port and unloaded aid pallets. French, Japanese and Chinese navy ships are also en route carrying aid.

The Tongan government has insisted on contactless delivery of aid, and all pallets unloaded from aircraft or ships are isolated for 72 hours before being distributed by the local emergency service.

At a press conference on Tuesday, Tongan authorities said the two workers at Queen Salote wharf who tested positive were vaccinated, and it was unknown if they had the Omicron variant.

-AAP