South Korean President Moon Jae-in has declared "war" against the coronavirus as the number of infections swelled beyond 5,000, ordering all government agencies to be on 24-hour alert and to boost their emergency response systems.

At a weekly Cabinet meeting yesterday, he revealed plans to provide 30 trillion won (S$34.9 billion) in funds to fight the virus, and called for a "bold fiscal injection" to cushion the economic fallout.

Finance Minister Hong Nam-ki warned that the virus outbreak could cut South Korea's economic growth by 0.2 percentage point this year. The central bank has revised its growth forecast for the country to 2.1 per cent - down from 2.3 per cent before the outbreak.

South Korea is the second most infected country after China, where the coronavirus originated. There are more than 80,000 cases in China alone.

Yesterday's increase of 851 new cases in South Korea brought the total number of infections to 5,186, with the death toll at 31. Thirty-four people have recovered.

More than half of all cases are linked to the Daegu branch of the secretive Shincheonji Church of Jesus. Over 2,700 of its members have tested positive for the virus after the first case - a 61-year-old woman with no recent travel history - emerged on Feb 18.

The Korea Centres for Disease Control and Prevention revealed yesterday it is investigating two Shincheonji members who travelled to Wuhan in January. One of them tested positive in end-February, but it is unclear if there is a direct link between this member and the mass outbreak in Daegu, an official said.

There are now 3,601 cases in Daegu, about half of whom are still waiting for a hospital bed in the overburdened healthcare system.

The health authorities are planning to open up public facilities to be used as treatment centres for some 2,000 patients by early next week.

Mr Moon said yesterday that the outbreak is in a critical phase. "The crisis in Daegu and North Gyeongsang province has reached a peak, and the whole country has entered a war against the infectious disease," he said.

More than 90 countries have imposed entry bans and quarantine requirements against visitors from South Korea, or are planning to do so, despite appeals from Seoul against such measures.

From today, Singapore will disallow travellers who have been to South Korea in the past 14 days to enter or transit through the country. Singaporeans, residents and long-term pass holders returning from South Korea will be issued a Stay-Home Notice for 14 days.