A "special care zone" has been set up in the South Korean city of Gyeongsan after it saw a spike in coronavirus cases.
Similar zones have been declared around neighbouring Daegu city and Cheongdo County, with face masks being provided and residents warned against travelling.
Health officials said dozens of newly commissioned military nurses are due to begin work in Daegu on Thursday to help the patients.
Meanwhile, the US military confirmed two new cases among relatives of its troops in the country.
It comes as Australia joined almost 100 nations to impose travel restrictions on South Koreans.
Trump touts $5,000 payout if Republicans win as Vance waits in wings
Search expands after Philippine ferry fire kills five and leaves dozens missing
Trump says Iran war to end after US midterm elections
US military says it struck vessel in Caribbean, killing 3
At least 14 killed in explosion at weapons depot in Syria
US hits five Iranian oil tankers after attack on Navy ships
UK gives air traffic provider a week to probe outage that halted flights
Serbia's President Vucic dissolves parliament, calls snap elections
