Reuters) - Japan, the world’s third-biggest economy, will close its borders to all foreigners, while Australia’s plans to re-open to skilled migrants were also in doubt as nations scrambled on Monday to rein in the spread of the Omicron variant of the coronavirus.

Markets regained some composure as investors await more details of the variant following a freefall last week after news of its emergence ignited fears that fresh curbs could upend a nascent economic revival from a two-year pandemic.

Potentially more contagious than prior variants, Omicron, first identified in South Africa, has been found in Australia, Belgium, Botswana, Britain, Canada, Denmark, France, Germany, Hong Kong, Israel, Italy, the Netherlands and South Africa.

It could take “days to several weeks” to understand the level of severity of the variant, says the World Health Organization (WHO), which has dubbed it a “variant of concern”.

Japan will close its borders to all foreigners from Tuesday, Prime Minister Fumio Kishida said.

“We are (taking measures) with a strong sense of crisis,” he had told reporters earlier, although no Omicron infections have yet been found in Japan.

Australia is to review plans to re-open from Dec. 1 to skilled migrants and students, Prime Minister Scott Morrison said on Monday, adding it was a “bit too early” to reinstate two-week hotel quarantine for foreign travellers.

“So we just take this one step at a time, get the best information, make calm, sensible decisions,” Morrison told broadcaster Nine News.

A national security panel will meet later in the day to assess border easing due from Wednesday, he added, while leaders of states and territories are set to meet.

Morrison called for calm as the severity, transmissibility and vaccine resistance of Omicron had not been determined, echoing remarks by the WHO.

Symptoms of Omicron are so far mild and could be treated at home, a South African doctor, one of the first to suspect a different variant, has said.