An Australian aid ship with a coronavirus outbreak docks in Tonga.

An Australian naval ship carrying aid supplies arrived in Tonga on Wednesday, a day after the Australian defense minister said that 23 people aboard the vessel had tested positive for the coronavirus.

The ship, the H.M.A.S. Adelaide, docked in Tonga early Wednesday evening, Sione Hufanga, the United Nations spokesman in the remote Pacific nation, said in a telephone interview.

“It’s in front of me now,” he said. No one was entering the vessel, he added, and its cargo was being offloaded by machines.

Two weeks ago, Tonga was slammed by the world’s largest volcanic eruption in decades, and a tsunami that followed. The country was smothered with ash and swamped with water, complicating efforts to deliver aid, particularly in remote islands.

At least three people were killed, and the scale of the disaster is still coming into focus, in part because the eruption cut off the nation’s lone connection to the internet. The outbreak on the Australian ship is stoking concerns that aid workers could inadvertently take the virus to Tonga, which reported its first case in October.

Japan’s national broadcaster reported on Wednesday that the country’s Defense Ministry had suspended its aid mission to Tonga because several members of the Japanese Air Self-Defense Force — which has been delivering aid to Tonga since Saturday from a base in Australia — had tested positive for the virus.

Tonga requires arriving travelers to quarantine for 21 days, and about 60 percent of the country’s population has received two doses of a Covid-19 vaccine.

The Australian ministers for foreign affairs, defense and international development said in a joint statement on Wednesday that the H.M.A.S. Adelaide had arrived in Tonga carrying helicopters, engineering equipment and medical and humanitarian supplies. They said it was “undertaking an entirely contactless delivery of humanitarian assistance and disaster relief supplies.”

Peter Dutton, Australia’s defense minister, had said at a news conference on Tuesday that the 23 people aboard the ship who had tested positive for the virus were in isolation.

“Under no circumstance will we compromise the health and well-being of those Tongans, who have already had a concerted effort against the virus,” he said.

Tonga has a population of about 100,000 people. Its geographical isolation — the country’s main island is 1,100 miles northeast of New Zealand — has largely helped it ward off a coronavirus outbreak.

The country’s lone Covid case of the pandemic came from a person who arrived in October on a commercial flight from Christchurch, New Zealand.