Yoon Tae-ho, an overall officer of disinfection at the Central Disaster Management headquarters, told a press briefing that strict quarantine measures will be enforced on arrivals from the United States beginning Friday midnight local time.
All South Korean and foreign nationals arriving from the United States for a long stay will be required to self-isolate for two weeks, while people showing symptoms will be tested for the virus.
Those who violate the quarantine rule will be sentenced to less than one year in prison, or fined less than 10 million won (8,100 U.S. dollars).
The country has implemented tighter screening procedures for arrivals from Europe since Sunday.
All people from Europe have got mandatory virus tests regardless of symptoms, and been placed under self-isolation for two weeks.
The tightened immigration procedures came amid the rising concern about the imported cases.
In the latest tally, South Korea reported 100 more COVID-19 cases for the past 24 hours, raising the total number to 9,137. The daily caseload steadied in recent days, but the imported infections showed signs of growing.
Of the new cases, 34 were detected at airports and 17 more imported cases were confirmed by local governments.