Authorities in Australia stepped up contact tracing and called for people in the city of Melbourne to come forward for coronavirus testing as the number of infections in a cluster linked to a quarantine hotel rose to 11.

More than 22,500 tests were done in the previous 24 hours in Australia's second most populous city and authorities scrambled to contain the spread of a highly transmissible variant of the virus from workers at a Holiday Inn, Reuters reported.

Three new cases were reported on Thursday, a manager at the hotel and the spouses of two members of staff, Victoria state authorities said. All 11 cases in the cluster were confirmed to have the variant of the virus that emerged in Britain.