Daegu, where 2.5 million people are asked to stay indoors, saw its confirmed cases jump by 131 to 457 on Monday morning, despite efforts to stem the spread of the virus, the Korea Centers for Disease Control and Prevention (KCDC) said in a statement.

Although health authorities voiced hope that the virus can be contained, experts said the virus may have spread more widely nationwide as cases with no clear links to China or confirmed cases continued to be discovered in Seoul and other regions.

Vice Health and Welfare Minister Kim Gang-lip told reporters, "If authorities fail to contain the spread of the COVID-19 in Daegu, there is a high possibility that COVID-19 could spread nationwide."

To beef up the first line of defense, authorities will swiftly find patients with mild symptoms and isolate them, Kim said.

Health authorities will check about 28,000 people in Daegu who have shown flu symptoms over the past two weeks, officials said.

Despite an alarming surge in confirmed cases in recent days, the government has no plan to expand entry bans on foreign nationals from China's other provinces, officials said.

Currently, South Korea bans foreign nationals entering the country from China's Hubei province, the epicenter of the virus outbreak.