Tokyo, Dec 22 (IANS): Japan reported its most likely first community spread of the Omicron variant of Covid-19 in Osaka Prefecture on Wednesday, with one infected person having travelled overseas recently and three family members being infected through unknown sources.

A man in his 30s with a recent history of travelling overseas was identified as a close contact. He had stayed in a designated quarantine hotel and later was confirmed to be infected with the Omicron variant, Xinhua news agency reported.

The three family members are a man and woman in their 30s and a girl under 10. They were admitted to the hospital between Saturday and Monday after developing mild symptoms, including fever.

The Osaka prefectural government has already identified close contacts of the family members, with health authorities conducting tests and monitoring their health condition.

Osaka Governor Hirofumi Yoshimura said it is most likely Japan's first case of community transmission as Japan steps up efforts to prevent entry of the Omicron variant through strict border controls.

Yoshimura called on residents to take measures to protect themselves from infection "on the premise that there are community spread infections in the prefecture."

Health Minister Shigeyuki Goto told reporters that the cases in the western region should be considered as a community transmission and the government will take all necessary precautions.

"At this point, we don't believe the Omicron variant is widespread in the country," Goto also noted.

Prime Minister Fumio Kishida said on Tuesday that Japan will extend the current border control measures "for the time being" through early January next year as the Asian country remains vigilant amid uncertainty over the mutant strain.