“The first priority here is to find every case in those towers, so that we don’t have an explosion of infections,” van Diemen said.
Victoria has ramped up testing and restrictions since a flare-up of cases last week.
Another two Melbourne neighborhoods were also told to stay at home from midnight Saturday, adding to the nearly 300,000 people put under restrictions on Tuesday.
The measures allow residents to leave their homes for essential reasons only, including for work and to buy food.
The lockdowns were a “difficult but important step” Deputy Chief Medical Officer Paul Kelly said, ahead of an emergency meeting of top health officials on Saturday evening.