(Adds comment from Premier)
SYDNEY, July 4 (Reuters) - Australia's second most-populous state, Victoria, reported its biggest jump in coronavirus cases since late March on Saturday, forcing the expansion of stay-at-home orders to more Melbourne suburbs and the complete lockdown of nine public housing towers.
The southeastern state recorded 108 new cases on Saturday, up from 66 on Friday and more than 70 new cases in each of the previous four days.
"These numbers are a very real concern to all of us," Victorian Premier Daniel Andrews told a news conference.
The spike in Victoria is being closely watched as the rest of the country has reined in the virus that causes COVID-19.
Australia's most populated state, New South Wales, reported six new coronavirus cases on Saturday, five of them returning travellers from overseas.
The sixth is a past infection and not an active case, according to health officials. The state reported no new cases on Friday.
Overall, Australia has weathered the coronavirus pandemic much better than most other nations, with just over 8,300 cases and 104 deaths so far.
The nine towers in Melbourne consists of 1,345 units, housing about 3,000 residents.
They will be locked down for at least five days, effective immediately, after many residents from those towers returned a positive COVID-19 test.
Police will be placed on each floor of the towers and law enforcement authorities will also control access points.
"These are very challenging times," Premier Andrews added.
"The alternative is this gets right away from us and we have not just 12 postcodes in lockdown but every postcode locked down. I don't want to get to that."