KOROR: The remote Pacific nation of Micronesia recorded its first case of Covid-19 on Monday, ending its run as one of the few places on Earth without the coronavirus.

President David Panuelo acknowledged the development was "alarming" for the country's 100,000 inhabitants but said the case had been contained at the border.

"For this reason, citizens across the nation should remain calm," he said in a televised address.

"Do not panic because the situation is contained."

Panuelo said the positive test came from a crewman on a government ship "Chief Mailo", which had been in the Philippines undergoing repairs.

He said the man and his colleagues remained on the vessel, which was anchored in a lagoon under round-the-clock surveillance.

"We remain in what we call Covid-condition-four, which means that schools, churches, and businesses of all kinds are still open," he added.

Far-flung Pacific island nations have been among the most successful in the world at keeping out the virus after closing their borders early in response to the threat, despite the huge cost to tourism-reliant economies.

Vanuatu, the Solomon Islands, the Marshall Islands, Samoa and now Micronesia have lost their virus-free status, although none have so far reported community transmission.

The island nations and territories of Kiribati, Nauru, Palau, Tonga and Tuvalu are believed to still be free of the coronavirus.

The cautious approach adopted in the Pacific islands was prompted by fears they are particularly vulnerable because of poor hospital infrastructure and high rates of underlying health conditions such as obesity and heart disease.