The Omicron variant is spreading quickly in Tonga in the wake of last month's volcanic eruption, with the number of detected COVID-19 cases having doubled to 64, AFP reported on Thursday.

Health Minister Saia Piukala said 31 new cases had been reported in the previous 24 hours, a record for the island nation that was virus-free until last month's blast. 

Piukala said samples sent to Australia confirmed the variant currently spreading is the highly-transmissible Omicron strain. The source of the initial infection remains undetermined.